The experimenter who does not know what he is looking for will not understand what he finds.

The doubter is a true man of science: he doubts only himself and his interpretations, but he believes in science.

[Those] who have an excessive faith in their theories or in their ideas are not only poorly disposed to make discoveries, but they also make very poor observations.

Man does not limit himself to seeing; he thinks and insists on learning the meaning of phenomena whose existence has been revealed to him by observation. So he reasons, compares facts, puts questions to them, and by the answers which he extracts, tests one by another. This sort of control, by means of reasoning and facts, is what constitutes experiment, properly speaking; and it is the only process that we have for teaching ourselves about the nature of things outside us.

True science teaches us to doubt and, in ignorance, to refrain.

Man can learn nothing unless he proceeds from the known to the unknown.

The experimenter who does not know what he is looking for will not understand what he finds.