On Symbols (-1799)

"Natural justice is a symbol or expression of usefulness, to prevent one person from harming or being harmed by another."  (Epicurus, "Sovereign Maxims"

"All teems with symbol; the wise man is the man who in any one thing can read another." Plotinus, The Enneads c. 250)

"Letters are signs of things, symbols of words, whose power is so great that without a voice they speak to us the words of the absent; for they introduce words by the eye, not by the ear." (Isidore of Seville, "Etymologiae", cca. 800-625)

"The Syllogism consists of propositions, propositions consist of words, words are symbols of notions. Therefore if the notions themselves (which is the root of the matter) are confused and over-hastily abstracted from the facts, there can be no firmness in the superstructure. Our only hope therefore lies in a true induction." (Francis Bacon, The New Organon, 1620)

"Nature's great book is written in mathematical symbols." (Galileo Galilei, "The Assayer", 1623)

"It is obvious that if we could find characters or signs suited for expressing all our thoughts as clearly and as exactly as arithmetic expresses numbers or geometry expresses lines, we could do in all matters, insofar as they are subject to reasoning, all that we can do in arithmetic and geometry." (Gottfried W Leibniz, 1677)

"In symbols one observes an advantage in discovery which is greatest when they express the exact nature of a thing briefly and, as it were, picture it; then indeed the labor of thought is wonderfully diminished." (Gottfried W Leibniz, [letter to Ehrenfried W von Tschirnhaus] cca. 1680)

"Algebra is a general Method of Computation by certain signs and symbols which have been contrived for the Purpose, and found convenient." (Colin Maclaurin, "A Treatise of Algebra", 1748)

As a general rule - never substitute the symbol for the thing signified, unless it is impossible to show the thing itself; for the child's attention is so taken up with the symbol that he will forget what it signifies." (Jean Jacques Rousseau, "Emile, or On Education", 1762)