If an opinion can eventually go to the determination of a practical belief, it, in so far, becomes itself a practical belief; and every proposition that is not pure metaphysical jargon and chatter must have some possible bearing upon practice.
It is often very illuminating...to ask yourself how you got at the facts on which you base your opinion. Who actually saw, heard, felt, counted, named the thing, about which you have an opinion?
Dixit 
