Plato

427-347 BC

came of a distinguished Athenian family. In his youth, as he tells us in a letter, he had looked forward eagerly to entering public life.Plato left behind him a mass of writings, of which we possess several letters and at least twenty-five authentic dialogues. These dialogues contain his answers to the three fundamental questions that had been raised by his predecessors and contemporaries. First, where can man find anything which he can know is truth ?
Second, what are the origin and constitution of the natural world in which man is set ? Third, for what purpose was man created and what should he choose as his aim in life ?

From Epicharmus, Plato >

But thus, it is – if to an even number,
Or even an odd one, if you prefer it,
You add a unit, or if you deduct one,
Say will the number remain the same?
Certainly not.

So, if you take a measure
A cubit long, and add another cubit,
Or cut a portion off, the measure then
No longer is the same?
Of course it is not.

Now turn your eyes and thoughts upon mankind –
We see one grows, another perishes :
So that they all exist perpetually
In a condition of transition. That
Whose nature changes must be different
At each successive moment, from the thing
It was before. So also, you and I
Are different people now from what we were
But yesterday;  and then, again, to-morrow
We shall be different from what we’re now ;
So that, by the same rule, we’re always different.