Deductive reasoning or deduction is the process of thinking from one or more statements (premises) to reach a logically certain conclusion (the type of logic used in hypothesis-based science); is a form of logical thinking that uses a general principle or law to forecast specific results.
In science, deduction is used to reach conclusions believed to be true. A hypothesis is formed; then evidence is collected to support it. If observations support its truth, the hypothesis is confirmed. In deductive reason, the pattern of thinking moves in the opposite direction as compared to inductive reasoning. From those general principles, a scientist can extrapolate and predict the specific results that would be valid as long as the general principles are correct.
Studies in climate change can illustrate this type of reasoning. For example, scientists may predict that if the climate becomes warmer in a particular region, then the distribution of plants and animals should change. These predictions have been made and tested, and many such changes have been found, such as the modification of arable areas for agriculture, with change based on temperature averages.
Both types of logical thinking are related to the two central pathways of scientific study: descriptive science and hypothesis-based science. Descriptive (or discovery) science, which is usually inductive, aims to observe, explore, and discover, while hypothesis-based science, which is typically deductive, begins with a specific question or problem and a potential answer or solution that can be tested. The boundary between these two forms of study is often blurred, and most scientific endeavors combine both approaches. The fuzzy boundary becomes apparent when thinking about how easily observation can lead to specific questions.