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 accidental causes of science are only accidents relatively to the intelligence of a man.

What a fearful object a long-neglected duty gets to be

If they are, then the only ultimate truths are the particulars of concrete experience, and no postulate or general assumption is inherent in science until its proceedings become systematic, or the truths already reached give direction to further research.

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

And we owe science to the combined energies of individual men of genius, rather than to any tendency to progress inherent in civilization.

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.