Nicomachean Ethics,

 c. 350 BC

If we take the various natural powers which belong to us, we first acquire the proper faculties and afterward display the activities. It is clearly so with the senses. It was not by seeing frequently or hearing frequently that we acquired the senses of seeing or hearing; on the contrary, it was because we possessed the senses that we made use of them, not by making use of them that we obtained them. But the virtues we acquire by first exercising them, as is the case with all the arts, for it is by doing what we ought to do when we have learnt the arts that we learn the arts themselves; we become builders by building and harpists by playing the harp. Similarly it is by doing just acts that we become just, by doing temperate acts that we become temperate, by doing courageous acts that we become courageous. The experience of states is a witness to this truth, for it is by training the habits that legislators make the citizens good. This is the object which all legislators have at heart; if a legislator does not succeed in it, he fails of his purpose, and it constitutes the distinction between a good polity and a bad one.

John Locke

Of the Conduct of the Understanding,


We are born with faculties and powers capable almost of anything, such at least as would carry us further than can easily be imagined; but it is only the exercise of those powers which give us ability and skill in anything that leads us toward perfection. The legs of a dancing master and the fingers of a musician fall as it were naturally, without thought or pains, into regular and admirable motions. Bid them change their parts, and they will in vain endeavor to produce like motions in the members not used to them, and it will require length of time and long practice to attain but some degrees of like ability. What incredible and astonishing actions do we find rope dancers and tumblers bring their bodies to! All these admired motions beyond the reach and almost conception of unpracticed spectators are nothing but the mere effects of use and industry in men whose bodies have nothing peculiar in them from those of the amazed lookers-on. As it is in the body, so it is in the mind: practice makes it what it is, and most even of those excellencies which are looked on as natural endowments will be found, when examined into more narrowly, to be the product of exercise, and to be raised to that pitch only by repeated actions. 

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