In the end we retain from our studies only that which we practically apply.
You acquire a language most readily in the country where it is spoken; you study mineralogy best among miners; and so with everything else.
The use of a thing is only a part of its significance. To know anything thoroughly, to have the full command of it in all its appliances, we must study it on its own account, independently of any special application.
Science has been seriously retarded by the study of what is not worth knowing and of what is not knowable.
If a man sets out to study all the laws, he will have no time left to transgress them.