After referring to Aristotle, and adducing some examples of foolish things believed by learned and common men alike, because they had not applied the tests of observation, he concludes: “Oportet ergo omnia certificari per viam experientiae.” He continues with something unexpected:
“Sed duplex est experientia: one is through the external senses, and thus those experimenta take place which are made through suitable instruments in astronomy, and by the tests of observation as to things below. And whatever like matters may not be observed by us, we know from other wise men who have observed them. This experientia is human and philosophical; but it is not sufficient for man, because it does not give plenary assurance as to things corporeal; and as to things spiritual it reaches nothing. The intellect of man needs other aid, and so the holy patriarchs and prophets, who first gave the sciences to the world, received inner illuminations and did not stand on sense alone. Likewise many believers after Christ. For the grace of faith illuminates much, and divine inspirations, not only in spiritual but corporeal things, and in the sciences of philosophy. As Ptolemy says, the way of coming to a knowledge of things is duplex, one through the experientia of philosophy, and the other through divine inspiration, which is much better.”[653]
Any doubt as to the religious and Christian meaning of the last passage is removed by Bacon’s statement of the
“seven grades of this inner science: the first is through illuminationes pure scientiales; the next consists in virtues, for the bad man is ignorant; ... the third is in the seven gifts of the Holy Spirit, which Isaiah enumerates; the fourth is in the beatitudes which the Lord defines in the Gospel; the fifth is in the sensibus spiritualibus; the sixth is in fructibus, from which is the peace of God which passes omnem sensum; the seventh consists in raptures (in raptibus) and their modes, as in various ways divers men have been enraptured, so that they saw many things which it is not lawful for man to tell. And who is diligently exercised in these experiences, or some of them, can certify both to himself and others not only as to spiritual things, but as to all human sciences.”[654]
These utterances are religious, and bring us back to the religious, or practical, motive of Bacon’s entire endeavour after knowledge: knowledge should have its utility, its practical bearing; and the ultimate utility is that which promotes a sound and saving knowledge of God. The true method of research, says Bacon in the Compendium studii,
“... is to study first what properly comes first in any science, the easier before the more difficult, the general before the particular, the less before the greater. The student’s business should lie in chosen and useful topics, because life is short; and these should be set forth with clearness and certitude, which is impossible without experientia. Because, although we know through three means, authority, reason, and experientia, yet authority is not wise unless its reason be given (auctoritas non sapit nisi detur ejus ratio), nor does it give knowledge, but belief. We believe, but do not know, from authority. Nor can reason distinguish sophistry from demonstration, unless we know that the conclusion is attested by facts (experiri per opera). Yet the fruits of study are insignificant at the present time, and the secret and great matters of wisdom are unknown to the crowd of students.”[655]
It is as with an echo of this thought, that Bacon begins the second chapter of his exposition of experimental science in the sixth part of the Opus majus, from which we have but now withdrawn our attention. He anxiously reiterates what he has already said more than once, as to the properties and prerogatives of this scientia experimentalis. Then he gives his most interesting and elaborate example of its application in the investigation of the rainbow, an example too lengthy and too difficult to reproduce. In stating the three prerogatives, he makes but slight change of phrasing; yet his restatement of the last of them:—“The third dignitas of this science is that it investigates the secrets of nature by its own competency and out of its own qualities, irrespective of any connection with the other sciences,”—signifies an autonomous science, rather than a method applicable to all investigation. The illustrations which Bacon now gives, range free indeed; yet in the main relate to “useful discoveries” as one might say: to ever-burning lamps, Greek fire, explosives, antidotes for poison, and matters useful to the Church and State. Along these lines of discovery through experiment, Bacon lets his imagination travel and lead him on to surmises of inventions that long after him were realised. “Machines for navigating are possible without rowers, like great ships suited to river or ocean, going with greater velocity than if they were full of rowers: likewise wagons may be moved cum impetu inaestimabili, as we deem the chariots of antiquity to have been. And there may be flying machines, so made that a man may sit in the middle of the machine and direct it by some devise: and again, machines for raising great weights.”[656] The modern reality has outdone this mediaeval dream.