A scientist is one who has learned to organize his knowledge. The main difference between a scientist and one who is not is that the scientist sees the significance of facts, while the non-scientific man sees facts as more or less unrelated things. As one comes to hunt for causes and inquires into the significance of things, one becomes a scientist. A thing or an event always points beyond itself to something else. This something else is what goes before it or comes after it, is its cause or its effect. This causal relationship that exists between events enables a scientist to prophesy. By care- fully determining what always precedes a certain event, a certain type of happening, a scientist is able to predict the event. All that is necessary to be able to predict an event is to have a clear knowledge of its true causes.
Whenever, beyond any doubt, these causes are found to be present, the scientist knows the event will follow. Of course, all that he really knows is that such results have always followed similar causes in the past. But he has come to have faith in the uniformity and regularity of nature.