Examples of deductive reasoning start from a general, factual premise and then progress to specifics that hold true based on the validity of the premise. The best examples use uncontested facts, such as the premise that all birds have wings. Deductive reasoning tells us that because all birds have wings, and a robin is a bird, then the robin has wings.
Deductive reasoning is a scientific method used to prove a hypothesis or deduct a truth based on logic. The process works only if the facts in the initial premise are sound and beyond debate. A major component of deductive reasoning is the assumption that if something is true for one member of a class or group, then the same thing is true for all members of that class. For example, if it is true that all normal dogs have four legs, and it is also true that a poodle is a dog, then a poodle has four legs. Likewise, because whales are warm-blooded, and orcas are whales, then orcas are warm-blooded. Deductive reasoning can also be applied to actions with a cause and effect. If Jennifer buys a pair of running shoes, and the shoes cost $100, then Jennifer now has $100 less in her bank account.