A is A

The law of causality is necessarily entwined with the law of identity. The law of identity states that an entity is what it is. A is A. It's pretty simple which is why it's so basic to the philosophy of truth. It also proves key to the battle against self-delusion.

An entity must always act in accordance with its nature. If it did not, it would not be that particular entity. For example, if I were told that a particular entity were a tiger, I would know that it is orange with black stripes and that I should not provoke it or be near it without some sort of protection. That is the nature of a tiger. If these things were not true about the entity then the entity in question is not a tiger.

The law of identity tears apart semantic arguments. A word like 'love' can mean different things to different people. This is one of the weaknesses of language. If we identify the nature of what we're talking about by stating the causal relationships that define the entity in question, there will not be any confusion about the entity being described. In mathematics or physics the law of identity is more straight-forward. If someone mentions the number pi then the audience can immediately think of many identifying characteristics of the entity: approximated by 3.14159 or 22/7, the convergence point of the Taylor series 4 * (1-1/3+1/5-1/7+1/9-...), the ratio of any circle's circumference to diameter, etc. Any number that does not meet all these criteria cannot be pi. And there are other characteristics of the number pi that are currently unknown but that does not mean that they cannot be known or that the characteristics have not always existed.

The identity of an entity is experientially defined. We come to know the nature of an object through interaction with it. In order to systematically deal with reality we must extrapolate upon our experience to predict future experiences with the same entity. We form what may be called prejudices or stereotypes. In a past experience I remember that I did not like tuna. I may extrapolate that I still do not like tuna. I may or may not be correct but I have a reference point. And as always, the eternalist craves to know when he is wrong so that he can correct himself and not be wrong in that point again.

Because we have finite experience with entities our knowledge of the nature of the entities is incomplete. We will be wrong from time to time in our assumption about the nature of the entities but we must start with what we know by experience and always be glad to gain more experience and more knowledge. As we gain more experience and more knowledge about an entity we will be wrong in predicting its nature less and less frequently.

A thing is what it is and cannot be other than what it is. A is A, A was A and A will always be A unless some causal force changes the nature of A into another entity defined by A and the nature of the causal force. Sawing a wood board in two creates two boards, not a chicken or a ship or anything else.