In no department of thought is the difference between the Greek and Roman mind more clearly seen; in none was the form more completely borrowed, and the spirit more completely missed. The object of Greek philosophy had been the attainment of absolute truth. The long line of thinkers from Thales to Aristotle had approached philosophy in the belief that they could by it be enabled to understand the cause of all that is. This lofty anticipation pervades all their theories, and by its fruitful influence engenders that wondrous grasp and fertility of thought [13] which gives their speculations an undying value. It is true that in the later systems this consciousness is less strongly present. It struggles to maintain itself in stoicism and epicureanism against the rising claims of human happiness to be considered as the goal of philosophy. In the New Academy (which in the third century before Christ was converted to scepticism) and in the sceptical school, we see the first confession of incapacity to discover truth. Instead of certainties they offer probabilities sufficient to guide us through life; the only axiom which they assert as incontrovertible being the fact that we know nothing. Thus instead of proposing as the highest activity of man a life of speculative thought, they came to consider inactivity and impassibility [13] the chief attainable good. Their method of proof was a dialectic which strove to show the inconsistency or uncertainty of their opponent's positions, but which did not and could not arrive at any constructive result. Philosophy (to use an ancient phrase) had fallen from the sphere of _knowledge_ to that of _opinion_. [15] Of these _opinions_ there were three which from their definiteness were well calculated to lay hold on the Roman mind. The first was that of the Stoics, that virtue is the only good; the second that of the Epicureans, that pleasure is the end of man; the third that of the Academy, that nothing can be known. [16] These were by no means the only, far less the exclusive characteristics of each school; for in many ways they all strongly resembled each other, particularly stoicism and the New Academy; and in their definition of what should be the practical result of their principles all were substantially agreed. [17]