<text><span class="style10">he Scientific Method (3 of 3)The ideal of science, and the practice</span><span class="style7">Full comprehensiveness is an ideal yet to be achieved. The two current leading theories, quantum mechanics (which explains atomic processes, see p. 26) and the general theory of relativity (which explains astronomical processes, see p. 26) are mutually inconsistent, although </span><span class="style26">both</span><span class="style7"> are firmly accepted by all physicists. But comprehensiveness remains an </span><span class="style26">ideal</span><span class="style7"> of physics, because physicists recognize this inconsistency as a problem requiring resolution.Surprisingly, a theory can be accepted as true even though it is known to make some false predictions. For example, it was well known in the 19th century that Newton's laws could not be squared with the precise orbit of the planet Mercury. However, because Newton's laws were so successful elsewhere, 19th-century physicists regarded Mercury's orbit as an unexplained anomaly that did not shake their belief in Newton's laws. Only after those laws had been superseded by the theory of relativity was the orbit of Mercury regarded as one of the facts that refuted Newton.</span><span class="style10">DEDUCTIVE AND INDUCTIVE INFERENCES</span><span class="style7">Here is a simple </span><span class="style26">deductive</span><span class="style7"> inference.Given the premises All rabbits are mammals.All mammals have kidneys. we </span><span class="style26">deduce</span><span class="style7"> the conclusion All rabbits have kidneys. The defining characteristic of a valid deductive argument is that it is </span><span class="style26">impossible</span><span class="style7"> for all the premises to be true and the conclusion false, because the information contained in the conclusion is already stored in the premises, taken collectively. Mathematical calculations are deductive inferences.Here is a simple</span><span class="style26"> inductive</span><span class="style7"> inference.Given the premise All observed ravens are black. we </span><span class="style26">induce</span><span class="style7"> the conclusion All ravens, whether observed or not, are black. The defining characteristic of an inductive argument is that the information contained in the conclusion </span><span class="style26">goes beyond</span><span class="style7"> the information contained in the premises. Hence it is </span><span class="style26">possible</span><span class="style7"> for inductive arguments to let us down - for their premises to be true but their conclusions false.Indeed, inductive inferences have been known to let us down. Once upon a time we were in a position to assert All observed swans are white. and hence to induce the conclusion All swans are white. But then black swans were discovered in Australia.Deductive inferences, no matter how long, have been codified and the rules for their validity worked out. Inductive inferences have resisted codification, and their validity is controversial.</span><span class="style26">Explanations</span><span class="style7"> of particular experimental results by theories use deductive inferences. </span><span class="style26">Justification</span><span class="style7"> of a theory by experimental results uses</span><span class="style26"> inductive</span><span class="style7"> inferences, although of a kind more complex than the simple example given.</span></text>
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<text><span class="style10">n experimental biochemical laboratory</span><span class="style7">. Many of the observed phenomena upon which scientists seek to build theories are in the form of specially designed experiments. Such experiments are often used to test a </span><span class="style26">hypothesis</span><span class="style7"> - a suggested explanation for a collection of known facts. If the experiments confirm the hypothesis, the hypothesis may be elevated to the more certain status of a </span><span class="style26">theory</span><span class="style7">. However, such a theory is never - in the strictest sense - a logical conclusion from the observed facts.</span></text>
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<text>ΓÇó THE HISTORY OF ASTRONOMYΓÇó THE HISTORY OF SCIENCEΓÇó THE HISTORY OF MEDICINEΓÇó PHILOSOPHY</text>
