And when all the world is overcharged with Inhabitants, then the last remedy of all is Warre, which provideth for every man, by Victory or Death. - Thomas Hobbes

It is not easy to fall into any absurdity, unless it be by the length of an account; wherein he may perhaps forget what went before. For all men by nature reason alike, and well, when they have good principles. For who is so stupid as both to mistake in geometry, and also to persist in it, when another detects his error to him? By this it appears that reason is not, as sense and memory, born with us; nor gotten by experience only, as prudence is; but attained by industry: first in apt imposing of names; and secondly by getting a good and orderly method in proceeding from the elements, which are names, to assertions made by connexion of one of them to another; and so to syllogisms, which are the connexions of one assertion to another, till we come to a knowledge of all the consequences of names appertaining to the subject in hand; and that is it, men call science. And whereas sense and memory are but knowledge of fact, which is a thing past and irrevocable, science is the knowledge of consequences, and dependence of one fact upon another; by which, out of that we can presently do, we know how to do something else when we will, or the like, another time: because when we see how anything comes about, upon what causes, and by what manner; when the like causes come into our power, we see how to make it produce the like effects. Children therefore are not endued with reason at all, till they have attained the use of speech, but are called reasonable creatures for the possibility apparent of having the use of reason in time to come.

So that in the first place, I put for a general inclination of all mankind a perpetual and restless desire of Power after power, that ceaseth only in Death. And the cause of this is not always that a man hopes for a more intensive delight than he has already attained to, or that he cannot be content with a moderate power: but because he cannot assure the power and means to live well, which he hath present, without the acquisition of more.

Understanding being nothing else, but conception caused by Speech.