I have recently been repeatedly confronted with the philosophical quandary of whether or not our perceptions of reality can be trusted, or if our internal models of the world around us are bound to be riddled with flaws and misrepresentations. A fellow blogger has spurred be to put down my thoughts in writing.

I think you have to begin by admitting that we can never know if our senses do justice to reality, because we have no other way to gauge their efficacy than by our senses themselves. However, ultimately, I think they do a pretty damn good job.

I’ve found evidence for this in the fact that a brain is, in its most basic form, an input-output system. Input stimulus: output response to stimulus. Evolution tunes the system to give the proper response to the proper stimulus, and therefore to be faithful to reality. For example, we have a vermicompost box, and when we want to get the worms to move in a certain direction, we expose them to light. They promptly wriggle in the direction of the nearest shade. If their flee response weren’t faithful to reality, they’d fry to death, or waste valuable energy wriggling when there was no sun.

Granted, the human brain is more sophisticated than that, because it has a complex intermediate step of model building based on memory. This apparatus allows synchronic tuning of responses to stimuli, as opposed to letting natural selection tune them. However it’s still just an elaborate version of “when the world is this way, respond in that way.”

Therefore, if you’re not building an accurate model of the world around you, then your brain isn’t performing its function. Evolution should then select for brains that make increasingly accurate models of the surrounding environment, or at least as accurate as any given organism needs (a human needs no sense for surface tension, but a water strider needs no sense for vertical orientation). Sure, there are glitches in the system, and they give rise to models that belie reality, but only in trivial ways: like optical illusions, pareidolia, and religion.

And there’s my daily epiphany: religion belies reality only in trivial ways. The belief that there is an invisible man in the sky who sees everything you do fits neatly into the gaps in our perception in such a way that it cannot be disproven, and it does not (often) dictate our reactions to stimuli. If it interfered with our model-building apparatus in either of these ways, evolution would have–and modern science could have–disposed of it quickly.

In closing, I’d like to analogize the brain to a house; the function of the brain is to construct models of the world, and the function of a house is to protect its inhabitants. You can build a house out of all kinds of things (aluminum, bricks, adobe etc.), and while you’ll have different engineering strategies based on the materials you are using–and different drawbacks with each–the end goal is still to create shelter (in the case of the brain, to build faithful models). Evolution set us on a particular path, with a particular set of materials–namely, the more basic reptilian and mammalian brains–and the drawbacks inherent thereto. The evolutionary history of the brain presents a unique set of obstacles to building a functional model-building apparatus, and has crucially informed its eventual architecture, in the same way selecting Play-Doh as the building material for your house would present a unique set of obstacles to its construction. Surely, it’d be better to choose bricks than Play-Doh, but evolution won’t let you switch materials mid-build, but we got as close as we could. Obviously, the materials we got stuck with weren’t that bad, because we’re still here. And our model building apparatus can’t be that bad either.