Antoine Lavoisier

“principle of acidity”

“which supposedly entered into chemical reactions (such as combustion) but had no weight. It was a radical step, therefore, for Lavoisier to base a system of chemistry on a balance of weights and to maintain that chemistry is not concerned with weightless”

“..when they perceive that a body which was before manifest to the senses has escaped and disappeared, they should not admit or liquidate the account before it has been shown to them where the body has gone to and into what it has been received.”

“We may lay it down as an incontestible axiom, that, in all the operations of art and nature, nothing is created; an equal quantity of matter exists both before and after the experiment; the quality and quantity of the elements remain precisely the same; and nothing takes place beyond changes and modifications in the combination of these elements. Upon this principle the whole art of performing chemical experiments depends: We must always suppose an exact equality between the elements of the body examined and those of the products of its analysis. p. 226”

“We must trust to nothing but facts : These are presented to us by Nature, and cannot deceive. We ought, in every instance, to submit our reasoning to the test of experiment, and never to search for truth but by the natural road of experiment and observation. pp. xviii”

“It is a maxim universally admitted in geometry, and indeed in every branch of knowledge, that , in the progress of investigation, we should proceed from known facts to what is unknown. ...In this manner , from a series of sensations, observations, and analyses, a successive train of ideas arises, so linked together, that an attentive observer may trace back to a certain point the order and connection of the whole sum of human knowledge. pp. xv”

“Thus, while I thought myself employed only in forming a Nomenclature, and while I proposed to myself nothing more than to improve the chemical language, my work transformed itself by degrees, without my being able to prevent it, into a treatise upon the Elements of Chemistry. p.xiv”

“We think only through the medium of words.”

“Here, then: a revolution [in science and chemistry] has taken place in an important part of human knowledge since your departure from Europe... I will consider this revolution to be well advanced and even completely accomplished if you range yourself with us. ...After having brought you up to date on what is happening in chemistry, it would be well to speak to you about our political revolution. We regard it as done and without any possibility of return to the old order. Letter to Benjamin Franklin (Feb 2, 1790) as quoted by I. Bernard Cohen , Revolution in Science”

“The Chain of Reason versus the Chain of Thumbs”