Parmenides' argument which I gave you last time is a peculiar one of this kind. It is an argument which gives you absolute certainty. You read that argument again, and we shall see what kind of certainty is involved in that argument. Let me read out once again: "Thou canst not know what is not", you can see the direct statement; "Thou canst not know what is not", this is a certainty; you can never know that which doesn't exist, you can know only that which exists. It is a very sweeping statement. You can be sure of this statement. And therefore he has put a parenthesis: "That is impossible". Absolutely certain, there is no question of doubt about it. So he picked up such a statement, such a datam that is clinching. This is what happens when you become true a philosopher. So many facts are given to you and you are able to pick up one datum which is sweeping. That is why people like to read philosophers, because philosophers are able, after a lot of thinking, after tremendous exercises of dealing with data, to pick up some such statements, and they are able to formulate them. This is the peculiarity of this argument: "Thou canst not know what is not - that is impossible - nor utter it; for it is the same thing that can be thought and that can be." It is a very simple statement actually, it says: if you examine your nature, you will always examine data in the light of your thought, it is the first thing that is said. Whatever you are going to decide, whatever you are going to judge, whatever you are going to know, it says first of all, it is by the instrument of thought that you will do it. This is the finding of the philosophers that thought is so constituted that it can only focuses upon that which exist. That which does not exist can never be applied to thought. Such is the nature of the thought. It is the key. Now this is an irrefutable statement because it describes the very nature of thought. So if you can find out the nature of thought, which is the instrument of knowledge at least at our present level, then you can be sure of this statement. For thought can be applied only to that which exists.
The second statement which is made - although yesterday I put it to you with some kind of force, at this next stage now when you are more mature today than yesterday - this second statement, when you examine it you will find fault with it, although it looks very much convincing and very clinching too, but you will find fault with it. It says: "How, then, can what is going to be in the future, or how could it come into being? If it came into being, it is not. Nor is it if it is going to be in the future. Thus is becoming extinguished and passing away not to be heard of. The thing that can be thought and that for the sake of which the thought exists is the same for you cannot find thought without something that is as to which it is uttered." This third statement is only a repetition of the first statement, it is clinching, but the second statement, the middle argument, although it may seen to be only an elucidation of the first, says something more and it is illegitimate. I will not ask you now to find out where is it this illegitimacy. Let it dwell in your mind for some time, we shall come to this second statement and find out where there is a fallacy in this argument. It is an argument which seems only a restatement of the first, but it is not. It is something much more.