They mistrust systems; they adhere closely to facts and the study of facts with their own senses.

As they do not easily defer to the mere name of any fellow-man, they are never inclined to rest upon any man's authority; but, on the contrary, they are unremitting in their efforts to point out the weaker points of their neighbors' opinions.

Scientific precedents have very little weight with them; they are never long detained by the subtilty of the schools, nor ready to accept big words for sterling coin; they penetrate, as far as they can, into the principal parts of the subject which engages them, and they expound them in the vernacular tongue.
Scientific pursuits then follow a freer and a safer course, but a less lofty one.
The mind may, as it appears to me, divide science into three parts.

The first comprises the most theoretical principles, and those more abstract notions whose application is either unknown or very remote.

The second is composed of those general truths which still belong to pure theory, but lead, nevertheless, by a straight and short road to practical results.