Every occurrence in Nature is preceded by other occurrences which are its causes, and succeeded by others which are its effects. The human mind is not satisfied with observing and studying any natural occurrence alone, but takes pleasure in connecting every natural fact with what has gone before it, and with what is to come after it.

If you ask me whether science has solved, or is likely to solve, the problem of this universe, I must shake my head in doubt. We have been talking of matter and force; but whence came matter, and whence came force? You remember the first Napoleon’s question, when the savans who accompanied him to Egypt discussed in his presence the problem of the universe, and solved it to their apparent satisfaction. He looked aloft to the starry heavens, and said—“It is all very well, gentlemen, but who made all these!” That question still remains unanswered, and science makes no attempt to answer it.

It is as fatal as it is cowardly to blink facts because they are not to our taste.

Newton’s passage from a falling apple to a falling moon was an act of the prepared imagination. Out of the facts of chemistry the constructive imagination of Dalton formed the atomic theory. Davy was richly endowed with the imaginative faculty, while with Faraday its exercise was incessant, preceding, accompanying and guiding all his experiments. His strength and fertility as a discoverer are to be referred in great part to the stimulus of the imagination.

The conclusion of Science which recognizes unbroken casual connection between the past and the present would undoubtedly be that the molten earth contained within it elements of life, which grouped themselves into their present forms as the planet cooled. … The difficulty and reluctance encountered by this conception, arise solely from the fact that the theologic conception obtained a prior footing in the human mind. Did the latter depend upon reasoning alone, it could not hold its ground for an hour against its rival. * * * Were not man’s origin implicated, we should accept without a murmur the derivation of animal and vegetable life from what we call inorganic nature. The conclusion of pure intellect points this way and no other.

The mutton in the study gathered over it a thick blanket of Penicillium. On the 13th [December 1875] it had assumed a light brown colour as if by a faint admixture of clay; but the infusion became transparent. The ‘clay’ here was the slime of dead or dormant Bacteria, the cause of their quiescence being the blanket of Penicillium. I found no active life in this tube, while all the others swarmed with Bacteria. In every case where the mould was thick and coherent the Bacteria died, or became dormant, and fell to the bottom of the sediment … The Bacteria which manufacture a green pigment appear to be uniformly victorious in their fight with the Penicillium.

There is, however, no genius so gifted as not to need control and verification. ... [T]he brightest flashes in the world of thought are incomplete until they have been proved to have their counterparts in the world of fact. Thus the vocation of the true experimentalist may be defined as the continued exercise of spiritual insight, and its incessant correction and realisation. His experiments constitute a body, of which his purified intuitions are, as it were, the soul.

To him [Faraday], as to all true philosophers, the main value of a fact was its position and suggestiveness in the general sequence of scientific truth.