[The contents of this chapter are discussed at much greater length in Modes of the Finite, Part 1, Section 1, Chapters 1-10]

1.1. What does "real" mean?

Consider the following excerpt from Carlos Castaneda's book The Teachings of Don Juan: A Yaqui Way of Knowledge:

Finally, before I left that evening, I had to ask him, "Did I really fly, don Juan?"

"That is what you told me. Didn't you?"

"I know, don Juan. I mean, did my body fly?" Did I take off like a bird?"

"You always ask me questions I cannot answer. You flew. That is what the second portion of the devil's weed is for.... What you want to know makes no sense. Birds fly like birds and a man who has taken the devil's weed flies as such..."

"As birds do?"

"No, he flies as a man who has taken the weed...."

"Then I didn't really fly, don Juan. I flew in my imagination, in my mind alone."

"...The trouble with you is that you understand things in only one way. You don't think a man flies; and yet a brujo can move a thousand miles in one second to see what is going on....So does he or doesn't he fly?" (Pp. 146-7)

It is clear from this passage that Castaneda, who had the previous night smeared himself with a paste made from "devil's weed" and experienced himself flying far above the ground, did not believe that he had really flown. But don Juan, the "brujo" or sorcerer, seemed to imply that he really did, but in a different sense of "really" from the what Castaneda had always believed was the only one.

Another of Castaneda's books dealing with his experiences with don Juan is called A Separate Reality.

• The question for us is this: Is there one reality for all of us, or are there many realities, to be approached by different modes of experience?

We should be clear what saying that there are many realities will imply: it could mean that the same thing could be "really" true and "really" false at the same time. That is, someone seeing Castaneda lying on the ground, perhaps writhing in an unconscious fit would tell him, "You were here all the time; you didn't fly." But if don Juan is right he could answer, "Perhaps wraps I was, but I was flying a hundred miles away just the same."

Now of course, you could save this from being a flat contradiction if you said that his body was there, but his "soul" or "mind" or something actually was somewhere else. But he experienced his body as up there; and on another occasion he experienced himself as turning into a crow for a while. If there is more than one reality, then his body was both where an observer might see it and not there but above the world; or in the other case, his body was a human body apparently asleep and simultaneously not a human body at all, but a crow's. Both of those statements would be really true; it would depend on which reality you were talking about.

On the face of it, at least, it would seem more comforting if we could establish that there is only one reality, even if we couldn't categorically decide which person's experience of it was the right one. Of course, if we can make some progress in that direction too, that is all to the good.

1.1.1. Relativism

Let's try to be clear on what is involved in this. It's confusing, but bear with me. If there is a separate reality for each person and what is true is true only for that person, then how can you make this statement?

What statement? The statement, "What is true is true only for the person who thinks it is true." Think about that. If you make the statement to anyone, you are assuming that it has to be true for everyone that what is true is true only for the person who thinks it is true. But then the statement is false for the person who says it, because he's saying that there's at least one statement (that one) that's true for everyone. So if the statement applies to everyone, it's false.

But then, suppose you say that it's true, but only for the person who says it. It can't be true for anyone else, as we just saw above. But then, it makes no sense as a general statement. "What's true is true only for the person who says it" is true only for me, and doesn't apply to anyone else. But that is the same thing as saying that there may be truths that are true for everyone, which means that it's false for you that what's true for you is true only for you and no one else. So if the statement doesn't apply to everyone, it's false even for the person who makes it.

So the statement is false if it's true for everyone, and false if it's true only for the person who says it.

That is, the statement is false.

There is no circumstance in which it can be true. It is the equivalent of saying, "It is true for everyone that nothing is true for everyone." But that very statement unsays what it says; so the person believes it is true simultaneously believes it is false. Not that it is false for someone else, but that it is false for him also, because he wants it to be true for everyone, but what he wants to be true for everyone is that there is nothing that is true for everyone.

Think about this carefully.

The reason I am stressing this, even though it seems total nonsense, is that people who don't think clearly actually believe it (without realizing that they don't believe what they believe if they believe it). In fact, you have been taught it for years and years.

Why? Because it sounds arrogant to say, "I know what's true, and if you think it's false, you're wrong." Who are you to tell me that? And it sounds "humble" and "tolerant" to say, "Well, if you think X is true, then fine. Who am I to disagree with you? You have as much right to your opinion as I have to mine."

You say, "Well, what's wrong with that?" You see, you have been well taught. What's wrong with it is that it's wrong if it's right. Why? Who says you have as much right to your opinion as I have to mine? Isn't it just your opinion that "you have as much right to your opinion as I have to mine"? Then who are you to tell anyone else what his rights or your rights or anyone's rights are? How can you claim that everyone has a right to his own opinion when that's just your opinion, and is true only for you?

So this "humble" and "tolerant" stance is actually trying to force down everyone's throat the arrogant and absolutist position that you know what the real truth about truth is: that there is no truth for everyone. But in that case, there is no truth for you either. So not only should you not be trying to tell this to anyone else, you shouldn't be trying to tell it to yourself, because if it's true it's false.

Think! Don't just feel, think!

Do you really want to believe the opposite of what you believe? Do you really want to go around not only saying what is false, but babbling complete nonsense, saying something that can't possibly be true?

• DEFINITION: Relativism is the position that holds (as true for everyone) that what is true is true only for the person who thinks it is true.

Relativism is stupidity, then. Stupidity disguised in fancy-sounding phrases, but in the last analysis, stupidity. It can't be true for everyone that nothing is true for everyone.

Another way of putting this stupidity is, "Well, everything depends on your point of view." Oh, really? Do you mean that only from your point of view everything depends on one's point of view? That is, either "Everything depends on your point of view" is true only from your point of view (and is false from the viewpoint that there are truths that hold good from any point of view--which means that not everything depends on your point of view), or it is true no matter what your point of view is; in which case it is false from its own point of view. Why? Because it admits that there is at least one thing (that everything depends on your point of view) which does not depend on your point of view. And so, no matter what stance you take on this, if everything depends on your point of view, then not everything depends on your point of view. Which is a stupid statement.

•Which means, of course, that there is at least one truth that is true for everyone, no matter what point of view he holds. Obviously, if it is false that everything depends on your point of view, then at least something doesn't.

Once again, use your head and go over this. Don't just say, "Well, that's your point of view." What I'm telling you is that it's yours too, whether you want to admit it or not--because you can only deny it by agreeing with it.

It may seem as if I am being harsh and arrogant, saying that only fools can be relativists, since I have said that relativism is a stupid position. But I don't necessarily mean that at all, since it is possible to be very bright and not to have thought things through, especially since everyone else, bright as well as not bright, seems to take relativism for granted as obviously (and so absolutely) true. Many of the most brilliant people in the world held some stupid positions, because it had never occurred to them to question them.

• Beware of translating a critique of what a person says or holds as a put-down of the person as a person.

One of the less attractive aspects of relativism, and fact, is this tendency of its advocates to accuse those who disagree with relativist dogma of disrespecting them as persons. This takes discussion about what the facts really away from an intellectual search for the truth and puts it onto a moral plane. In the last analysis, which is worse, my telling you you are mistaken, or your telling me that I am evil?

But remember, it is not that the relativist disagrees with other people, but that he disagrees with himself. He wants it to be true that everything depends on your point of view, but he does not want this position to be true only from his point of view.

There are a couple of other variations on this same theme: "There are two sides to every story." Oh yes? Then are there two sides to "there are two sides to every story"? If so, then there is at least one story that does not have two sides. If not, then there is at least one story that does not have two sides. Figure this out for yourself. Again, I believe it was Chief Justice Oliver Wendell Holmes who said, "Every generalization is not worth a damn, including this one." So he was explicitly telling people not to pay attention to what he was saying, because what he was saying was not worth a damn. And people actually consider his generalization profound! But be clear, no matter who said it, it is not profound, but stupid.

• So what have we learned so far? That not everything depends on your point of view. Therefore, it is possible to arrive at objective truth, truth which is true for everyone, whether they realize it or not.

1.1.2. Self-evidence

But the knowledge that something-or-other is objectively true doesn't tell us what that something is. And since the mere belief that something is true doesn't make it true, then we need some criterion for finding out what is true and what isn't.

Actually, we have already found one criterion, the most powerful of all: if a position turns out to be false if it is true, then it must necessarily be false (because it is false if it is false, and false if it is true). Therefore, its opposite must necessarily be true. Thus, we saw that if everything depends on your point of view, Then not everything depends on your point of view; and so it must necessarily be true that not everything depends on your point of view. Such a truth is called "self-evident."

• DEFINITION: A statement is self-evident if its denial affirms it.

Evidence in general is the objective reason why we think that something is true. We have discovered that there are some statements that have to be admitted as true, because you can only say that they are false if you admit that they are true. So they are their own evidence. For instance, as we saw, to deny that not everything depends on your point of view can only be done if the denial does not depend on your point of view.

So something is not self evident because everyone agrees that it is true, or because no one questions its truth. People may question self-evident truths, but that does not make them not self-evident. It just means that the questioners are not thinking clearly (because implicitly they are agreeing with what they say they disagree with). Similarly, there are things that everyone agrees with that are by no means self evident: for instance Thomas Jefferson's statement in the Declaration of Independence, "We hold these truths to be self-evident: that all men are created equal..." Whatever the actual truth of the proposition, it is still quite possible to say that there are inequalities among human beings without doing so as a conclusion from the fact that all human beings are equal. So the proposition that all men are created equal is either true or false, but it is not proved true if it is called false, which is the criterion for self-evidence.

1.1.3. Immediate evidence

Now there is another criterion for truths, called immediate evidence: That is, I was there and I saw it with my own eyes. In other words, immediate evidence is the evidence of your own senses.

• DEFINITION: something is immediately evident if it is directly perceived.

The trouble with immediate evidence is that, while basically valid and true, it is not infallible, because our eyes and ears sometimes play tricks on us. Thus, we can think that something is true, and even have immediate evidence that it is true, but it is possible for it to be false. That was what happened to Carlos Castaneda at the beginning of this chapter. He had immediate evidence that he turned into a crow and flew away, but he had a good reason for saying that in fact he did not do so: First, because there is lot of evidence for saying that it is impossible for a human being to turn into a crow, and secondly because he had ingested a psychedelic drug, which was bound to distort his perceptions.

Self- evidence does not have this flaw, because a self evident proposition can not be false in any circumstances. Of course, the problem with self- evident propositions is that they are all trivial. It would be nice if we could just start from some self evident proposition and then just deduce everything from this proposition.

René Descartes, in fact, tried this around 1600 and ushered in Modern Philosophy with it, since he thought he had succeeded in showing how all kinds of truths were logically implied in what he thought was a self-evident truth, "I think, therefore I am." Unfortunately, he leaped to a number of conclusions that were not logically entailed in his first truth--and in fact the first truth itself involved a conclusion that was not logically warranted.

Why? It is self-evident that if I think, there is thinking going on; but does it logically follow that there is an "I" other than the thinking that is doing the thinking? Maybe "I" (as some philosophers have held) is just the stream of thoughts itself, and there is no "I" who is doing the thinking. True, when I experience myself thinking, I seem to be different from the thoughts I am thinking; but this is immediate evidence, not self-evidence.

We will see that this immediate evidence is correct; but what I am saying here is that it's not self-evident. It is possible to deny it without admitting it.

But before I go on, let's see where we've got so far. We know these facts, because they're self-evident: (1) There are at least some truths that are true for everyone, and don't depend on your point of view. (2) Some truths are self-evident. We also know that there's at least one other kind of evidence, which we generally accept as the truth, but which it is possible to be mistaken about: immediate evidence: what we directly perceive.

1.2. Evidence

But precisely because it's so easy to make something up and cook up "evidence" to say that it exists, we have to be very careful here. We have to have a very clear idea about what evidence is and what counts as evidence, and why, or we're back to just making statements and having one opinion be as good as another.

So first let's look at what evidence in general is. When do you ask for evidence, and what are you asking for? Well, you ask for evidence when a person makes a statement that he claims is true, and you doubt whether it really is true or not. So evidence is another word for the reason why a person thinks some given thing is true (or a fact).

With self-evidence, the reason why you think the statement is true is the statement itself. What it says is such that if you try to claim that it's false, you can only do so by admitting that it's true. With immediate evidence, you say, "I'm right here looking at it. I could be dreaming, but I know I'm not."

But with any other kind of evidence, what the person who asks for evidence is asking for is some other fact that will prove that what you say has to be true.

What does this mean? First of all, it means in practice that this other fact has to be admitted to be a fact by the person who's asking for the evidence. Either it's self-evident, or he also has immediate evidence for it, or he has some other evidence for it; but anyway, he knows it's a fact. So that's the first criterion of evidence: It has to be known to be a fact.

But the second criterion is this: It has to be able to be shown that if the statement to be proved were false, then the evidence (for some reason) couldn't be a fact.

Let me take an example. This writing you are now reading is evidence of my existence (not necessarily that I exist now as you read this, but at least that I at one time existed). As far as the writing is concerned, you have immediate evidence that it's here in front of you. But it wouldn't be here unless someone put these words on paper (or on whatever you're reading it from). And obviously "I" am (for purposes of this argument) "the one who put these words on the paper." Words just don't appear spontaneously on paper.

The point is, of course, that it's (for practical purposes) impossible for you to be reading this if I didn't exist; and therefore, the writing is evidence that I exist(ed).

So what we've got again is a case that if so-and-so is not true then something that's true is false. And that's not possible; and so so-and-so not only is true, it must be true.

• DEFINITION: Evidence is a known fact which implies another fact.

• DEFINITION: One thing implies another when it is contradictory to deny the second while admitting the first. That is, you could, of course, (physically speaking) deny the second statement, but you have in fact already logically affirmed it, because it has to be true if the first is true. So your "denial" would be meaningless.

Note that this is just what implication in general is. What the grounds for a given implication are isn't specified here. There may be many reasons why you know that the second statement has to be true if the first one is; and in fact, our next task is to explore how this happens. This will lead us, in the next chapter, into a discussion of scientific method and its generalization, metaphysical method.

1.2.1. The Principle of Contradiction

To approach this, let me begin by stating the basic law of all thought, which in fact we have been using in the whole discussion so far: the Principle of Contradiction.

• The Principle of Contradiction: What is true is not false in the respect in which it is true (logical formulation). What is is not what it is not (ontological formulation).

Strictly speaking, this should be called the Principle of Non-Contradiction (and many people in fact give it this name) because it says that there are no contradictions. Many other people (including the ones who taught me), however, call it the Principle of Contradiction, so that's what we'll call it here. But it means that contradictions are nonsense and can't be true. In fact, we can restate it in this way:

There are no real contradictions.

Or, in a third formulation,

Contradictions occur only in language.

But these two formulations require a definition:

• DEFINITION: A contradiction is a statement that affirms and denies the same thing. That is, a statement that says that something is both true and false, or that something isn't what it is. (The word comes from the Latin contra, against, and dicere, to say.)

The point is that you can state a contradiction, like "I am not now writing what I am writing," because language is such that we can string words together according to the rules of grammar; but you can't think a contradiction, and there can't really be any contradictions. That is, you can't think the equivalent of this sentence: "I am not thinking what I am thinking," because when you're thinking you know what you're thinking, and so you're aware of what you are thinking, and that it is what it is. Similarly, it's impossible for something to be what it isn't while it is what it is. So contradictions can't exist in thought or in reality, but only in language.

I hasten to say that a thought can't directly contradict itself, as I just said, but you can think a thought which implies something that contradicts it (without realizing the implication). Thus, relativists think that their position is true, without realizing that if it's true, then there's something (relativism itself) which is true for everyone, which means (by implication) that relativism is false. The implication which contradicts the relativist "principle" is hidden in the principle itself, and so people who don't think things through can hold the principle without realizing that they're implicitly contradicting themselves.

The Principle of Contradiction, of course, is another self-evident truth, because if you try to deny it, you can only do so by tacitly admitting it to be true. Why? Because if you say that it's false, you are asserting (as true and not false) that it's false. But the denial of the statement is the equivalent of saying that what's true can be false while it's true. But how can you assert this as true and not false? If it's true that what's true is false because it's true, then that means it's just as likely to be false that what's true is false because it's true. So you're talking nonsense, and again saying the opposite of what you're saying. (Sorry about this, if you're confused; but when people talk nonsense and you record it, what you put down doesn't make sense. Your job is to go back over this paragraph and "unpack" it to see just how the denial denies itself.)

The point is that the Principle has to be true; you can't even honestly entertain the idea that it's false.

Don't get the impression that there's anything profound about this Principle; it is absolutely trivial. It is the minimum necessary for any statement (or any thing) to make sense. It just says that, as I was point out above, though you can string words together so that they say the opposite of what they say (like, "This statement is false," which would be true if it's false and false if it's true), you can't think the "thought" that the words would correspond to, and there can be no "fact" that they would correspond to (because it would not be what it is). What is is what it is.

The difference between the "logical" and the "ontological" formulations of the Principle are that the first applies to our knowledge or speech (logos in Greek), while the second applies to the reality which we know ("ontology" comes from the Greek n, ontos, being, reality, and logos again, but now in the sense of "study of" or "science of").

This Principle was first formulated as such by the Greek philosopher Aristotle, around 350 B. C., though of course it has been used by everyone who has ever done any thinking from the very beginning.

Now of course, the Principle may seem sometimes to be false, because things can be false in one sense and true in another, or false at one time and true at another; and that is why the phrase "in the sense in which it is true" is added to the Principle. For instance, there is print on this page (within the margins) and there isn't print on this page (outside the margins); but that's not a contradiction. Or it is true (now) that there is print on this page; but when I was writing these words into my computer I could then say "It is false that there is print on this page," and that would have been a true statement. But that's not a contradiction either. The point of the Principle is that something which is true can't be false when it's true and in the way in which it's true.

The philosopher Georg Hegel in the 1800s built his theory on a kind of "denial" of the Principle, because he said that, while it's true in the abstract, still, in the concrete things "contain their own opposites suspended within them." For instance, when I say that John is a man, then (since John is not humanity itself, and James is also a man), then the mere fact that I have said that John is a man implies that John is not a man. There's more to John than just humanity (he's tall, and tallness is not humanity, for instance). So the concrete John is both a man and not a man.

This is, of course, true (and not false); but the point of the Principle (which Hegel doesn't deny) is that it is false that John is not a man insofar as he is a man. Hegel just doesn't like "insofar as," because it's abstract, and he wants to deal with the concrete. But that doesn't mean that the concrete falsifies the abstract; it just means that the abstract isn't the whole truth about anything. After all, if you put ten additional dollars into your wallet, you don't make the twenty that were already there disappear. So there's no problem with the Principle because of what Hegel said. The Principle of Identity

While we're at it, let me give a couple of variations of this Principle. One of them I stated just a while back.

• The Principle of Identity. What is true is true (logical formulation). What is is what it is (ontological formulation).

This again is self-evident, because its denial would have to be made on the basis of a statement that said what it said (which is what the Principle asserts). This is built into our thinking from the very beginning. I remember my three-year-old son looking out of the car window as we were driving along and saying, "There's a cow!" I replied that it looked to me as if it was a horse, and he answered, "Well if it's a cow, it's a cow." The Principle of Identity in action.

This is called a "necessary" truth. That is, what is necessarily is what it is. It's impossible for it to be anything else (as long as it is what it is). This "necessity," of course, doesn't mean that the thing can't become something else or even that it doesn't have any control over what it is; it's just (as my son said) if it is what it is, then it can't be false that it is what it is.

That is, my choice to be writing at this moment is a free choice, which means that it could have been a different one if I wanted it to. But the choice "necessarily" is what it is, given that in fact I made it. This "necessity-of-a-fact-to-be-what-it-is-while-it-is-what-it is" is called logical necessity.

• DEFINITION: Something is logically necessary if its denial involves you in a contradiction.

• DEFINITION: Something is physically necessary if it is impossible to prevent it.

There are people who confuse logical and physical necessity. Since things necessarily are what they are, they say, then they couldn't be any different--and so, they conclude, it doesn't matter what we do; things necessarily will be what they will be. But logical necessity is trivial; it just means that in fact, what is is what it is (and nothing else), not that a given thing has to be the way in fact it is and couldn't have been any different. There are a lot of things you can control, so don't let the abstract Principle of Identity fool you into thinking that "self-evidently" you can't do anything about your life. The Principle of the Excluded Middle

There's another variation on the Principle of Contradiction and/or the Principle of Identity called the Principle of the Excluded Middle:

• The Principle of the Excluded Middle: There is no middle ground between truth and falseness (logical formulation). There is no middle ground between being something and not being that thing (ontological formulation).

That is, if a statement is true, it's not "halfway into truth." Either it's true or it isn't. Now this does not exclude "half-truths," of course, which are true in one sense and false in another, because in the sense in which they are true they are completely true (and not "halfway true'), and in the sense in which they are false, they are utterly false. The whole sentence is "halfway true" in the sense that it is partly true and partly false, but no in the sense that it's got halfway to the truth without getting there.

Similarly, there are things that are not fully developed, such as a child. But the child is only halfway a man, not "halfway what it in fact is." Either it is what it is, or it isn't; it can't both be and not be what it is, or be neither what it is nor what it isn't.

We are going to see some apparent denials of this Principle; but in fact (in the abstract, if you want) they don't really deny it; it's just that if you aren't careful in what you're saying, it can look as if something is not completely what it is. Nevertheless, reality as it actually exists is (as you will discover) very mysterious indeed.

But this leads us to effects, causes, and scientific and metaphysical method, which is what the next chapter is about.

1.3. Opposites

But there is one further thing before we leave the Principle of Contradiction and its variations: There are different kinds of opposites.

• DEFINITION: Contradictories are opposites in the sense that if one of them is false, the other necessarily is true.

• DEFINITION: Contraries are "opposite ends of a scale," which admit of locations on the scale between them, neither of which is the extreme.

Black and white, for instance, are contrary opposites. There are shades of gray which are neither black nor white. This does not deny the Principle of the Excluded Middle, of course, since if the object is gray, it is neither black nor white, but it's not "neither gray nor not gray." (This is why I said that the Principle of the Excluded Middle has to be applied carefully.)

Black and non-black, however, (where "non-black" means "anything except black") are contradictory opposites, since if something isn't black, then it's not black, which is the same thing as saying it's non-black. Gray is non-black, blue is non-black, E-flat is non-black, heat is non-black, liberty is non-black; only black is not non-black.

Thus, contradictory opposites "divide the universe," as it is said, because of the Principle of the Excluded Middle. Contrary opposites, however, do not: "Not everything is black or white."

So if you're going to think clearly, be careful when people go from denying one opposite to affirming the other. This works if the opposites are contradictory, but not if they're contrary. For instance, no less a person than Plato committed this mistake in the Phaedo when Socrates says that life has to come from death, because life has to come into existence from "its opposite" (in the sense that if it begins to live, it clearly wasn't living before), and the opposite of life is death. No, the contrary of life is death; the contradictory of life is non-life. A living thing can (in principle) come into existence from, let us say, something inanimate (non-living); but that doesn't mean it came into existence from what's dead.

Summary of Chapter 1

Some people think that reality is what you experience, and since different people experience different things, then it seems that there isn't one reality for all of us, but a different reality for each point of view. This position is called "relativism.

But relativism can't be true, because it makes the general statement, "What is true is true only for the person who thinks it is true," is a general statement, supposed to be true for everyone, which means that it is false. This is a variation on "Everyone has a right to his own opinion," which implies that a person who dares to say that someone else's false opinion is false is "dissing" that person, putting him down. This confuses facts with morals. Thus, relativism is false if it is true. Thus, it is self-evident that there is at least one thing that is true for everyone, and which does not depend on your point of view.

Something is self-evident when its denial affirms it. It is impossible for a self-evident truth to be false, because there is no way you can say that it's false without admitting that it's true. Something is immediately evident if it is directly perceived. We know that, generally speaking, what is immediately evident is true, but we also recognize that our senses can play tricks on us. Only what is self-evident cannot possibly be false.

Evidence is a known fact that implies another fact. One thing implies another when it is impossible to deny the second one while admitting the first one. The criteria for something to be evidence is (a) that it be known to be a fact, (b) that it be connected to something else in such a way that the other thing has to be a fact if the evidence is a fact. This definition does not tell us what the grounds for the connection is; we will learn some later.

To approach this, we need first to know the basic principle of all thought: the Principle of Contradiction, which states that (logical formulation) what is true is not false in the respect in which it is true, or (ontological formulation) what is is not what it is not. Another way of putting this is that there are no real contradictions, or contradictions occur only in language. You can state a contradiction, but you can't think it and it can't exist. A contradiction is a statement that affirms and denies the same thing. The Principle is self-evident, since if you try to deny it, you must do so on the basis of something you declare to be true and not false. Aristotle first formulated the Principle. Georg Hegel apparently denied it, but not really, since he admits that "in the abstract" it holds good, and no one says that a concrete reality can't contain contradictory properties in different parts of itself.

A variation of this is the Principle of Identity, that what is true is true (logical), or what is is what it is (ontological). This is a "necessary" truth in the sense that it is self-evident (you can only deny it on the basis of something you hold to be true). This kind of necessity is logical necessity, which means that its denial involves you in a contradiction. This is opposed to physical necessity, which means that it is impossible to prevent the thing. Be careful not to confuse the two. The fact that your choice, for instance, is what it is does not mean that you had no control over what it would be.

Another variation is the Principle of the Excluded Middle that there is no middle ground between truth and falseness (logical) or there is no middle ground between being something and not being that thing. This Principle does not deny "half-truths" which are complex statements part of which are true and part false (or which are true in one sense and false in another); the truth is not "half-true" insofar as it is true. Similarly, there can be undeveloped things, such as a child, which are not fully what they will or can be; but they are (fully) what they are.

Finally, there are two different kinds of opposites: contradictory opposites (contradictories), in which if something is not one of the opposites, it necessarily is the other (because the other is defined to mean "anything except the first"), and contrary opposites, (contraries) which are opposite ends of a scale with degrees in between them. Thus, a thing can be neither contrary (since it can be one of the degrees in between); but it can't be neither of a pair of contradictories.