Causation, Perception, Morality, and the Domain of Science

The definition of science (as in physics, chemistry, biology, etc.) could be stated as something like “systematic knowledge of the physical or material world gained through observation and experimentation” (one of dictionary.com’s several definitions of the word “science”). This means that whatever cannot be observed in the physical world and tested experimentally lies outside the realm of what science can answer. Science can answer questions such as “what is the charge-to-mass ratio of an electron?” or “how does this wavefunction change in time?” or “why do the seasons go through an annual cycle?” All of these questions are asking for no more than physical information about the physical world: “How” is to be read as “in what [physical] way?” and “why” is to be read as “what is the physical cause?” This is what science deals with – the physical world. But when it comes to anything other than observation of physical reality, science must remain silent. Let’s look at a couple examples.

First, science assumes that when we study the physical world, what we perceive to be a physical reality outside of our own minds is indeed real, but this is a philosophical claim. No observation of the world could confirm that what we perceive is anything more than an illusory perception, but we assume that it is. Equivalently, the claim that our perceptions are illusions cannot be falsified through science, because science necessarily depends on perception. (You would have to rely on your perceptions to disprove them - it be like trying to pick yourself up off the ground by pulling on your hair.) An even more basic assumption made by science is that the logic and reasoning of our minds is an accurate guide to truth – without making this philosophical assumption, science can say nothing. There is no objective, unbiased frame of reference from which we could observe our own reasoning – we could not say the reasoning of our minds is reliable except by using our minds, and that is begging the question. In short, science cannot prove, but must simply assume, that our perceptions and rational thoughts are (in general) reliable.

As another example, consider the philosophical idea of causation. Science can observe that an apple falls in consistently the same way under a certain set of circumstances. Nevertheless it cannot prove that gravity (via the mass of the earth) actually causes the apple to fall. If causation is real, it is a physically unobservable phenomenon since it refers to connections between events and not to the physical events themselves. Causation cannot be perceived with our five senses, so it cannot be proved or disproved with science, and thus saying that causation is real is a philosophical statement.

In both of these cases, we make certain reasonable philosophical assumptions – assumptions that seem highly likely but that cannot be confirmed by experiment. Other assumptions of this kind could include moral statements, eg. “genocide is wrong.” Because moral right and wrong is not, like an electron or molecule, physically observable, it cannot be tested scientifically, yet we know that genocide is wrong.

In general, anything that cannot be fully perceived and understood physically is beyond the domain of science. Love, beauty, moral values, good and evil, suffering, death, existence, meaning and purpose – these are facts about the world that cannot be described in terms of particles and fields and dimensions. They lie outside the domain of science. There are many questions that could never be answered merely by pointing to something in the physical world. What is the meaning of death? Why is human nature both good and bad? Why is there suffering and evil in the world? These questions can be given partial answers by pointing to physical things such as the decaying of the human body, processes in the brain that result in a person being desensitized to violence, or events in the nervous system that cause sensations of pain or pleasure, moral repugnance or admiration of beauty.* But the larger question of why these remarkable realities are part of the world at all, and what purpose they serve, cannot be addressed by the scientist alone.

*See my posts on evolution, of which this is the first.