In the scale of life there is a gradual decline in physical variability, as the organism has gathered into itself resources for meeting the exigencies of changing external conditions; and that while in the mindless and motionless plant these resources are at a minimum, their maximum is reached in the mind of man, which, at length, rises to a level with the total order and powers of nature, and in its scientific comprehension of nature is a summary, an epitome of the world.

Such evidence is not the only kind which produces belief; though positivism maintains that it is the only kind which ought to produce so high a degree of confidence as all minds have or can be made to have through their agreements.

By what criterion... can we distinguish among the numberless effects, that are also causes, and among the causes that may, for aught we can know, be also effects, - how can we distinguish which are the means and which are the ends?

The very hope of experimental philosophy, its expectation of constructing the sciences into a true philosophy of nature, is basedon induction, or, if you please, the a priori presumption, that physical causation is universal; that the constitution of nature is written in its actual manifestations, and needs only to be deciphered by experimental and inductive research; that it is not a latent invisible writing, to be brought out by the magic of mental anticipation or metaphysical mediation.

Let one persuade many, and he becomes confirmed and convinced, and cares for no better evidence.

We receive the truths of science by compulsion. Nothing but ignorance is able to resist them.

Science asks no questions about the ontological pedigree or a priori character of a theory, but is content to judge it by its performance; and it is thus that a knowledge of nature, having all the certainty which the senses are competent to inspire, has been attained--a knowledge which maintains a strict neutrality toward all philosophical systems and concerns itself not with the genesis or a priori grounds of ideas.