Ideally, scientists deduce conclusions from general laws that they know to be true. For example, if we know that massive objects attract each other because of gravity, then it follows that an apple will fall to the ground when it releases from the tree. This logical reasoning from general to specific is known as deductive reasoning.

Often, however, we do not know the general laws that guide natural systems. We observe, for example, that birds appear and disappear as a year goes by. Through many repeated observations in different places, we can infer that the birds move from place to place.

We can develop a general rule that birds migrate seasonally. Reasoning from many observations to produce a general rule is inductive reasoning. Although deductive reasoning is more logically sound than inductive reasoning, it only works when our general laws are correct. We often rely on inductive reasoning to understand the world because we have few immutable laws.

Sometimes it is insight, as much as reasoning, that leads us to an answer. Many people fail to recognise the role that insight, creativity, aesthetics and luck play in research. Some of our most important discoveries were made not because of superior scientific method and objective detachment, but because the investigators were passionately interested in their topics and pursued hunches that appeared unreasonable to fellow scientists.