981. Unfortified by the light of science, the practical man has no other assurance for the success of the future, than the experience of the past, and no resource for unforeseen events but ordinary expedients; he thus resorts to rules drawn from precedents, which, of course, can apply only to peculiar cases, instead of resorting to general principles which are capable of being applied to every case. Industry may be baffled, and hope defeated, by a thousand contingencies from causes incident to every process of art, and to every operation of nature. By these the mere routine-practitioner is deranged, or thrown off his guard; whilst the man of science refers events to their true causes, suggests the adaptation of measures to meet every case; and knowing the laws of nature to be immutable, operates on her materials with confidence in the result. Science alone, however, without practical experience, will not insure success, and may at first end in disappointment. But 'where theoretical knowledge and practical skill,' as Dugald Stewart observes, 'are happily combined in the same person, the intellectual power of man appears in full perfection, and fits him equally to conduct with a masterly hand the details of ordinary business, and to contend successfully with the untried difficulties of new and hazardous situations.' (Elements of the Philosophy of the Human Mind, 2d edit. p. 232.)
