When any affection is infused by sympathy, it is at first known only by its effects, and by those external signs in the countenance and conversation, which convey an idea of it.
— from A Treatise of Human Nature by David Hume

Whatever we do we should keep up the Chearfulness of our Spirits, and never let them sink below an Inclination at least to be well-pleased: The Way to this, is to keep our Bodies in Exercise, our Minds at Ease.
— from The Spectator, Volume 1 Eighteenth-Century Periodical Essays by Steele, Richard, Sir

In a word, I much doubt whether it be possible for a cause to be known only by its effect (as you have all along supposed) or to be of so singular and particular a nature as to have no parallel and no similarity with any other cause or object, that has ever fallen under our observation.
— from An Enquiry Concerning Human Understanding by David Hume

Javert was the first to alight; he made sure with one glance of the number on the carriage gate, and, raising the heavy knocker of beaten iron, embellished in the old style, with a male goat and a satyr confronting each other, he gave a violent peal.
— from Les Misérables by Victor Hugo

The town is also noted for a variety of articles of cabinet work and lacquered ware of the ordinary sort, and the room next to our apartment had been converted into a kind of bazaar in expectation of our arrival.
— from A Diplomat in Japan The inner history of the critical years in the evolution of Japan when the ports were opened and the monarchy restored, recorded by a diplomatist who took an active part in the events of the time, with an account of his personal experiences during that period by Ernest Mason Satow

It seems hardly credible while I am writing it down, but it is certainly true, that this same man, who has all the fondness of an old maid for his cockatoo, and all the small dexterities of an organ-boy in managing his white mice, can talk, when anything happens to rouse him, with a daring independence of thought, a knowledge of books in every language, and an experience of society in half the capitals of Europe, which would make him the prominent personage of any assembly in the civilised world.
— from The Woman in White by Wilkie Collins

In a word, I much doubt whether it be possible for a cause to be known only by its effect (as you have all along supposed), or to be of so singular and particular a nature, as to have no parallel and no similarity with any other cause or object that has ever fallen under our observation.
— from The Philosophy of Natural Theology An Essay in confutation of the scepticism of the present day by William Jackson

Let us henceforth keep our birthday in each other's company."
— from Tales From Jókai by Mór Jókai

Later there arose a disposition to speculate as to that which lies beyond sense and known only by its effect on sensible things.
— from The Universe a Vast Electric Organism by Geo. W. (George Woodward) Warder

If a species of Crustacean, with the above-described alternating method of reproduction (heterogeny), were killed off by its enemies on a larger scale than before, it is obvious that the threatened extinction of the species could be checked by the attainment of a correspondingly greater degree of fertility.
— from Essays Upon Heredity and Kindred Biological Problems Authorised Translation by August Weismann

This kind of beauty is especially conspicuous, even rising into dignity, in the poem called the Haunted Palace.
— from Life Without and Life Within; or, Reviews, Narratives, Essays, and Poems. by Margaret Fuller

For keeping off birds, insects, etc., from the fields by magic.
— from Castes and Tribes of Southern India. Vol. 2 of 7 by Edgar Thurston

Consciousness, as the Latin root of the word indicates, is the knowledge of being in existence.
— from The Positive Outcome of Philosophy The Nature of Human Brain Work. Letters on Logic. by Joseph Dietzgen

{120} Though we by no means ought to rank these with positive and substantial beauties, yet it must be allowed, that a knowledge of both is essentially requisite towards forming a complete, whole and perfect taste.
— from Fifteen Discourses by Reynolds, Joshua, Sir