Once upon a time, philosophers would debate whether God was a deceiver or not. Descartes pondered on this for decades, because he saw that our senses can deceive us, and so why would God not deceive us in other ways? In the end, he decided that God was not a deceiver. Today, most people would not consider that this is a meaningful question. However, common sense does not serve us at all well in our understanding of the world and how it works. And because it is so difficult to understand the world, the lazy appeal to intuition. So let me give a few examples of how our common sense and our intuition do not help us understand the world.
Imagine you go to the doctor with some unusual symptoms. The doctor does some tests, and a few days later he tells you that you have a rare disease. By rare, I mean maybe one in a thousand people suffer from this condition. He tells you that the test has a 90% accuracy for people who have the disease. In other words, if 10 people with the disease were tested the results would come back as positive for nine of them. What is the probability that you have the disease? The immediate answer would be 90%. But that would be the wrong answer. The probability that you have the disease is only 10% or less. Most doctors are aware of this kind of thing, and so where rare diseases are concerned they will insist on additional tests. To understand why you only have a 10% probability of having the disease, even though the test is 90% accurate would require an understanding of Bayes rule. It’s difficult and completely unintuitive and so I’m not going to go there.
For another example let’s look at Einstein and his theory of relativity. Intuitively we all think that time passes at the same rate for all of us. This is not true. If someone accelerates away from you and reaches very high velocity their time will pass more slowly than yours. When they come back you may have aged 50 years, and they may have only aged a few days. Common sense and intuition do not serve us at all well in understanding this.
It seems likely that most of what we think we understand, is flawed. The amount of work that goes into uncovering even the simplest misunderstandings is huge. So the nature of the universe as far as mankind is concerned, is that it is almost certainly completely different from our superficial understanding of it. And it seems that the deeper we probe, the more perverse is its nature.
And so I think that Descartes was quite justified in asking whether God was a deceiver. Based on the hard work of a few thinkers who have managed to unravel reality to some extent, I think the answer to that would probably be yes; God is a deceiver.