How Can We Trust Our Senses?

Experience the world. Empiricism is the idea that we learn through our experiences, and these experiences derive exclusively from sense impressions. An empiricist can say: a) "We know that out senses 'pick up' what is really out there"; or b) "We should act 'as if' this were the case."

Begin with faith. The idea that we have little choice than to act "as if" our senses pick up what is really out there dispenses with the inconvenient problem of proving this. A utilitarian can say that it does not matter whether we really sense things or are just "brains in a jar," getting impulses placed into our brains that simulate actual experience. Our happiness and livelihoods depend on our reacting to and learning from what we perceive. Whether or not we are "brains in a jar" is irrelevant.

Think inwardly. St. Augustine and Rene Descartes tried to solve this problem of existence in a similar way. Both writers said that we can be absolutely certain that we exist, since to deny this would be to affirm it. If I deny that I exist, then the denier must exist. Therefore, we know we exist with certainty. This also means that absolute truth is real and possible. Since we exist, we also know that we are contingent and nonself-sufficient. Therefore, we did not make ourselves. We are dependent on an objectively existing world that has brought us into existence and nourished us --- a world we did not create. From the concept of the "I," these two philosophers deduced the objective reality of the external world.

Think about what reality would be like without the existence of our minds. Immanuel Kant wrote in the late 18th century that the external world exists because our minds contain categories that "filter" experience. Things like space and time are not "out there" but are products of our mind. Space and time, and all that follows from them, are "imposed" on the chaos of sense impressions to create stable objects. This view revolutionized philosophy forever.

Consider the role of the human ego --- which is the same as the will --- in creating the external world. In the very early 19th century, the German school of epistemology was born in response to Kant. Writers like Johann Fichte developed the theory that the "out there" is really a function of the human mind. We know the "out there" only because it affects our ego. In fact, the "out there" is a product of the ego --- an ego striving for ethical fulfillment. The "out there" is the ego positing itself, we see things that our own selves have created. Since the ego is the same everywhere in all people, our experience is not just from ourselves --- it is not just a subjective fantasy --- but is an intersubjective reality. We agree on what exists because our collective ego has experienced it.