Observation lies at the basis of the thinking which leads to invention in the arts, to discovery in the domain of science, to productivity in the fields of literature, journalism, and oratory. It lies at the foundation of success in the professions and in the ordinary walks of life. The medical school, for instance, seeks to develop the power of noting facts and making careful observations. It encourages the student to put his observations on paper while the patient is before him, to compare the diseased or injured part with the corresponding healthy part, and to watch symptoms as a basis for a correct diagnosis of the case to be treated.
Books.
Daily life.
The use of the encyclopædia, if pursued without any attempt to verify its statements, may destroy the habits of observation which are so essential to correct thinking. Mere reliance on books cannot beget trustworthy habits of thought, for books contain the errors, as well as the wisdom, of the ages. Errors of judgment may be corrected by thinking; errors of fact must be corrected by observation. Many a book is made useless by new observations and discoveries. “Send to the cellar as useless every book on surgery that is eight years old,” said the professor to the librarian of a great university. The order is an indication of the rapid advances which science is making under the influence of observation, experiment, hypothesis, and verification. Observation is needed not merely to extend our scientific knowledge, but far more imperatively to acquaint us with our environment. We cannot learn from books the multitudinous details of business, or of our daily life. Books cannot make us acquainted with the circle of friends in which we move, the pupils whom we teach, the things in dress, toilet, and behavior upon which our standing and reputation very largely depend. No thinker has a right to neglect these. Many a famous professor has diminished his usefulness by carelessness in the observation of such details. The worst failures in the class-room are due to failure in observing either the difficulties or the conduct of the pupils. If conduct is to be regulated, it must be observed; if difficulties are to be explained, the teacher must perceive when and where they occur.
Men noted for their absent-mindedness nevertheless owe much of their fame and success to their ability to make accurate observations in favorite lines of study. Notwithstanding the many ludicrous tales about Newton’s failure to see ordinary conditions and circumstances, he showed himself indefatigable in watching the effect of a glass prism upon the ray of light admitted into a dark room. The falling of an apple started in his mind a train of thought which led to the discovery of the law of gravitation.
Experiment.
Daguerre.
Our best thinking is based upon experience, and our two main sources of experience are observation and experiment. How does experiment differ from simple observation? In the latter we watch conditions, phenomena, and sequences as they follow one another in the ordinary course of nature. In an experiment we change or control the course of nature by varying the conditions and causes for the sake of seeing the effects produced. In experiment the relation of causes and effects is studied by adding or excluding one factor after another. Take the discovery which made Daguerre famous. Up to his time men had tried in vain to fix the impression of the image formed in the camera obscura. No alchemist ever went to work at a more unpromising task than the one Daguerre set before himself. “As years rolled on, the passion only took deeper hold upon him. In spite of utter failures and discouragement of all kinds, for years in loneliness and secrecy, suspected of mental weakness even by his wife, he kept on in the same line of experiment.” Finally an accident gave him a clue to discovery. The plates with which he experimented were stowed away in a rubbish closet. One day he found, to his surprise, upon one of these plates the very image which had fallen upon it in the camera. Something in the closet must have produced the effect. He removed one thing after another, getting the same effect, until nothing remained except some mercury which had been spilled upon the closet floor. This was inferred to be the agent which developed the image, and thus was laid the foundation of the modern art of photography.[20]
Accidental observations.
The observation of a fact often stimulates thought in new directions. In fact, new sciences have arisen from accidental observations. “Erasmus Bartholinus thus first discovered double refraction in Iceland spar; Galvini noticed the twitching of a frog’s leg; Oken was struck by the form of a vertebra; Malus accidentally examined light reflected from a distant window with a double refracting substance; and Sir John Herschel’s attention was drawn to the peculiar appearance of a solution of quinine sulphate. In earlier times there must have been some one who first noticed the strange behavior of a loadstone, or the unaccountable motions produced by amber. As a general rule we shall not know in what direction to look for a great body of phenomena widely different from those familiar to us. Chance, then, must give us the starting-point; but one accidental observation well used may lead us to make thousands of observations in an intentional and organized manner, and thus a science may be gradually worked from the smallest opening.”[21]