to himself a method in accordance with observation, but he should take heed not to reduce observation to mere notion, to substitute words for this notion, and to use and deal with these words as if they were things. He should be acquainted with the labours of philosophers, in order to follow up the phenomena which have been the subject of his observation, into the philosophic region.
717.
It cannot be required that the philosopher should be a naturalist, and yet his co-operation in physical researches is as necessary as it is desirable. He needs not an acquaintance with details for this, but only a clear view of those conclusions where insulated facts meet.