What position have experiments performed, and may they play, in physics? How does one come to think rationally in experimental effects? The forget of scan makes an attempt to supply solutions to either one of those questions. Professor Franklin's method combines the certain examine of 4 episodes within the heritage of 20th century physics with an exam of a few of the philosophical matters concerned. The episodes are the invention of parity nonconservation ( or the violation of reflect symmetry) within the Fifties; the nondiscovery of parity nonconservation within the Nineteen Thirties, whilst the result of experiments indicated, no less than looking back, the symmetry violation, however the importance of these effects was once now not discovered; the invention and reputation of CP ( mixed parity-charge conjugations, paricle-antiparticle) symmetry; and Millikan's oil-drop test. Franklin examines some of the roles that scan performs, together with its position in identifying among competing theories, confirming theories, and calling fo new theories. the writer argues that you can actually supply a philosophical justification for those roles. He contends that if scan performs such vital roles, then one should have strong cause to think in experimental effects. He then offers with deveral difficulties touching on such reslults, together with the epistemology of scan, how one involves think rationally in experimental effects, the query of the impact of theoretical presuppositions on effects, and the matter of medical fruad. This unique and significant contribution to the examine of the philosophy of experimental technological know-how is an outgrowth of decades of study. Franklin brings to this paintings greater than a decade of expertise as an experimental high-energy physicist, with his major contributions to the background and philosophy of science.