(1) Facts are the foundation of all inductive generalizations. Induction is largely a matter of building general notions from individual notions derived from the observation of facts. (2) Observation is the act of watching the phenomena as they may occur. It involves the voluntary concentration of consciousness on the case in hand. (3) Experiment is the act of making phenomena occur for the purpose of watching for effects. It is in reality a form of observation which necessitates a manipulation of circumstances. (4) The average man is not given to careful observation. The rules adopted by scientific observers are: (1) The observation should be _precise_; (2) should concern only the material circumstances; (3) should be varied; (4) should be isolated. For the sake of _precision_ many instruments have been invented and methods devised; notably instruments for accurate measurements, such as the balance and thermometer, and methods like the method of averages. Frequently a situation may be so complicated as to demand a “preadjustment of attention.” With the untrained this very preadjustment may lead to serious error. An “all-angled observer” is the most trustworthy. (5) Errors in observation come from preconceived ideas; confusing perception with inference; ignoring the exceptions; sympathy; inattention; and a fallible memory. (6) An hypothesis is a supposition advanced for purposes of explanation and proof. (7) An hypothesis is a tentative induction. As soon as it is deprived of its tentative nature it ceases to be an hypothesis. (8) Hypothesis and theory are often used interchangeably when reference is made to phenomena of low probability. Theory should be used only in instances of high probability. (9) A permissible hypothesis must be (1) conceivable; (2) capable of proof or disproof; (3) adequate; (4) simple; (5) must not contradict any verified truth. (10) The hypothesis is especially serviceable in these four particulars: (1) as a working basis; (2) as a guide to ultimate truth; (3) as a discoverer of immediate truth; (4) as affording probable explanations. (11) There are certain characteristics which an honest and courageous investigator needs to possess. These are: (1) undoubted ability as an accurate observer of facts, (2) a constructive imagination, (3) a passion for truth. To build an acceptable hypothesis without fact is as impossible as it is to build a house without a foundation. The genius, because of his imaginative insight, transforms the simple fact into a complex invention or law. A prevailing “_intellectual dishonesty_” suggests the need of “_a greater passion for truth_.” =14. REVIEW QUESTIONS.= (1) Show that facts are the raw material of induction. (2) Define and illustrate a fact. (3) Define induction in terms of the notion. (4) Define and illustrate observation. (5) Define and illustrate experiment. (6) Show the difference between observation and experiment.