Scientific Method, term denoting the principles that guide scientific research and experimentation, and also the philosophic bases of those principles. Whereas philosophy in general is concerned with the why as well as the how of things, science occupies itself with the latter question only, but in a scrupulously rigorous manner. The era of modern science is generally considered to have begun with the Renaissance, but the rudiments of the scientific approach to knowledge can be observed throughout human history.

Definitions of scientific method use such concepts as objectivity of approach to and acceptability of the results of scientific study. Objectivity indicates the attempt to observe things as they are, without falsifying observations to accord with some preconceived world view. Acceptability is judged in terms of the degree to which observations and experimentations can be reproduced. Scientific method also involves the interplay of inductive reasoning (reasoning from specific observations and experiments to more general hypotheses and theories) and deductive reasoning (reasoning from theories to account for specific experimental results). By such reasoning processes, science attempts to develop the broad laws—such as Isaac Newton's law of gravitation—that become part of our understanding of the natural world.

Science has tremendous scope, however, and its many separate disciplines can differ greatly in terms of subject matter and the possible ways of studying that subject matter. No single path to discovery exists in science, and no one clear-cut description can be given that accounts for all the ways in which scientific truth is pursued. One of the early writers on scientific method, the English philosopher and statesman Francis Bacon, wrote in the early 17th century that a tabulation of a sufficiently large number of observations of nature would lead to theories accounting for those operations—the method of inductive reasoning. At about the same time, however, the French mathematician and philosopher René Descartes was attempting to account for observed phenomena on the basis of what he called clear and distinct ideas—the method of deductive reasoning.

A closer approach to the method commonly used by physical scientists today was that followed by Galileo in his study of falling bodies. Observing that heavy objects fall with increasing speed, he formulated the hypothesis that the speed attained is directly proportional to the distance traversed. Being unable to test this directly, he deduced from his hypothesis the conclusion that objects falling unequal distances require the same amount of elapsed time. This was a false conclusion, and hence, logically, the first hypothesis was false. Therefore Galileo framed a new hypothesis: that the speed attained is directly proportional to the time elapsed, not the distance traversed. From this he was able to infer that the distance traversed by a falling object is proportional to the square of the time elapsed, and this hypothesis he was able to verify experimentally by rolling balls down an inclined plane.

Such agreement of a conclusion with an actual observation does not itself prove the correctness of the hypothesis from which the conclusion is derived. It simply renders the premise that much more plausible. The ultimate test of the validity of a scientific hypothesis is its consistency with the totality of other aspects of the scientific framework. This inner consistency constitutes the basis for the concept of causality in science, according to which every effect is assumed to be linked with a cause.

Scientists, like other human beings, may individually be swayed by some prevailing worldview to look for certain experimental results rather than others, or to "intuit" some broad theory that they then seek to prove. The scientific community as a whole, however, judges the work of its members by the objectivity and rigor with which that work has been conducted; in this way the scientific method prevails.