We must recognize that the attempt to set forth the temporal course commonly referred to as the "evolution of mankind" is merely an attempt to structure events for convenient accessibility. Consequently, we must exclude from our discussion as far as possible such misleading notions as "development" and "progress. "
While the dogmatist is harmful, the sceptic is useless. . . ; one is certain of knowing, the other of not knowing. What philosophy should dissipate is certainty, whether of knowledge or of ignorance. Knowledge is not so precise a concept as is commonly thought. Instead of saying 'I know this', we ought to say 'I more or less know something more or less like this'. . . . Knowledge in practical affairs has not the certainty or the precision of arithmetic.
This great increase of the quantity of work which, in consequence of the division of labour, the same number of people are capable of performing, is owing to three different circumstances; first, to the increase of dexterity in every particular workman; secondly, to the saving of the time which is commonly lost in passing from one species of work to another; and lastly, to the invention of a great number of machines which facilitate and abridge labour, and enable one man to do the work of many.