We at the height are ready to decline.
There is a tide in the affairs of men
Which, taken at the flood, leads on to fortune;
Omitted, all the voyage of their life
Is bound in shallows and in miseries.
On such a full sea are we now afloat,
And we must take the current when it serves,
Or lose our ventures. (IV.ii.269?276)
Here, Brutus conceives of life as influenced by both fate and free will: human beings must be shrewd enough to recognize when fate offers them an opportunity and bold enough to take advantage of it. Thus, Brutus believes, does man achieve a delicate and valuable balance between fate and free will.
This philosophy seems wise; it contains a certain beauty as well, suggesting that while we do not have total control over our lives, we do have a responsibility to take what few measures we can to live nobly and honorably. The only problem, as the play illustrates over and over again, is that it is not always so easy to recognize these nudges of fate, be they opportunities or warnings. The characters? repeated failures to interpret signs correctly and to adapt themselves to events as they unfold form the basis for most of the tragedy that occurs in the play.