Deductive Reasoning

Deductive reasoning, or deduction, is the type of logic used in hypothesis-based science. In deductive reasoning, the pattern of thinking moves in the opposite direction from inductive reasoning. It uses a general principle or law to predict specific results. From these general principles, a scientist can predict specific results that remain valid as long as the general principles are correct.

For example, a researcher can make specific predictions from the hypothesis "butterflies are attracted to specific flowers based on petal color." These deductive tests are often written as "If...then" statements: if the hypothesis is true, then changing the flower's petal color should change the butterfly's attraction. Features like scent or petal shape should not affect attraction if color is the main factor, and these can be kept the same or tested separately.

These predictions are used to design experiments that test the hypothesis.

Although deductive reasoning is central to hypothesis-driven science and inductive reasoning is mostly linked to descriptive science, both forms of logic are important in research and often work together in the same experiments. In this example, the researcher might also notice that butterflies tend to avoid flowers with pointed petals. This observation can lead to a new inductive hypothesis, which can then be tested using deductive reasoning.