Observation and Experiment
In the philosophic sense, observation shows, and experiment teaches. Men sometimes seem to confuse experiment with observation. But man does not limit himself to seeing; he thinks and insists on learning the meaning of the phenomena whose existence has been revealed to him by observation. But certain physiologists and physicians characterize observation and experiment somewhat differently. The word observation in the singular, in its general and abstract use, means noting a fact accurately with the help of appropriate studies and means of investigation. Observation, then, is what shows facts; experiment is what teaches about facts and gives experience in relation to anything. The art of investigation is the cornerstone of all the experimental sciences. Now experimental reasoning is absolutely the same, whether in sciences of observation or in experimental sciences. Men who gather observations are useful only because their observations are afterward introduced into experimental reasoning; in other words, endless accumulation of observations leads nowhere.