This present scene of man's existence, this that we call nature, the stage on which mortal life begins and goes on and ends, the faculties with which man is equipped to act, to enjoy, to create, to hold his way amid or against the circumstances and forces round him--this is what each wants to know, as thoroughly and really as can be.

It is not to reduce things to a theory or a system that they look around them on the place where they find themselves with life and thought and power; that were easily done, and has been done over and over again, only to prove its futility.

It is to know, as to the whole and its parts, as men understand _knowing_ in some one subject of successful handling, whether art or science or practical craft.

This idea, this effort, distinguishes these two men.
The Greeks--predecessors, contemporaries, successors of Aristotle--were speculators, full of clever and ingenious guesses, in which the amount of clear and certain fact was in lamentable disproportion to the schemes blown up from it; or they devoted themselves more profitably to some one or two subjects of inquiry, moral or purely intellectual, with absolute indifference to what might be asked, or what might be known, of the real conditions under which they were passing their existence.

Some of the Romans, Cicero and Pliny, had encyclopaedic minds; but the Roman mind was the slave of precedent, and was more than satisfied with partially understanding and neatly arranging what the Greeks had left.