How do we know our minds are reliable?

There has been a recent odd argument that, if our brains are the product of evolution in which survial is the only “goal”, then we can not have any certainty that our mental processes are generating true conclusions. I responded to this notion on a Facebook thread begun by a Christian apologist recently.

Thanks for a well-formulated response, Nancy.

You asked how I know rational thought is a valid means of knowing truth.

Suppose you find an old compass in the middle of the woods. You want to know whether it functions reliably. What should you do? Do you attempt to discover the manufacturer of the compass? Probably not. Do you need to know how the compass ended up in the middle of the woods? I doubt it.

All you need to do is to test the compass. To the degree that the compass gives you sufficient predictive power to successfully navigate your way through the woods, to that degree you are justified in your confidence in the reliability of the compass.

The same is true for rational thought and our minds that process rational thought. To the degree that rational thought succeeds in accomplishing our goals, to that degree we are warranted in placing a matching degree of confidence in rational thought and our minds that process that rational thought. We don’t need to know anything about the origin of our brains to test them.

And there are all kinds of various tests we can perform. We can test our minds for their ability to recognize faces (strong) or to calculate probabilities (weak). Our brains are not always accurate, but to the degree that our brains have successfully generated the predictive power that makes our lives better, to that degree we can place confidence in our minds and the rational tools that we have also tested in conjunction with that mind.

So, I’m not sure what to make of this claim that, unless you know the source of your brain, you can’t trust it. Simply test it! Stop looking for the manufacturer of the compass, and just test it! You don’t need to believe in either a god or evolution to know whether your brain and tools of rationality work. Just test them. To the degree that they work, to that degree your confidence in them is warranted. I really don’t understand the confusion on this.

Here, try this. Imagine yourself waking up in a room without memory of a past life. You don’t know at that time how accurate your brain is. Also in the room are instructions and materials for assembling a ladder. What should you do? Fret all day that you don’t know whether you can trust your mind or the instructions? No. You take your mind and the instructions, and attempt to construct the ladder. If the end result is a stable ladder, then that degree of success is where you position your degree of confidence in your brain and in the instructions. Simple.

Note that epistemic honestly does not require that we find the truth in every instance, for there may be someone intentionally deceiving us. The only thing the epistemically honest individual needs to do is to follow the evidence as he or she perceives it. No cherry-picking. No epistemic cheating through a faith switch.


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