The problem that secularist logic faces is called Münchhausen Trilemma or Agrippa's Trilemma. The Münchhausen Trilemma has never been solved, but it has been buried and ignored. According to this trilemma, there are only three possible foundations for thought: unsupported assertion, infinite regression, or circular reasoning. It is rare to hear this trilemma discussed, because it destroys the validity philosophy, science, and any other possible thought about reality when using a Naturalistic worldview. Naturalism assumes that there is no spiritual realm and leaves only three possible foundations for thought.

If unsupported assertion, infinite regression, or circular reasoning were the only three options, no matter which of these three are chosen, nothing can be known. This does hold in a Secularist worldview. A secularist can never rationally say that he or she knows anything. They can never rationally claim that there are laws of logic or laws of nature. The Münchhausen Trilemma, sometimes called Agrippa's Trilemma, is a long-standing, well-known problem with thinking. Baron Münchhausen lived from 1720 to 1797 and borrowed the Trilemma from Agrippa the Skeptic, who probably lived in the later part of the First Century A.D.

However, the Münchhausen Trilemma is self-refuting in that it is either based on unsupported assertion, infinite regression, or circular reasoning. Since none of these foundations of thought have any strength, and since a chain of thought is only as strong as its weakest link, the Münchhausen Trilemma has no strength. In other words, we cannot know that it is true.

The Münchhausen Trilemma is a false trilemma. In the same way that a false dilemma is a fallacy giving only two choices when at least one additional choice is possible, this false trilemma is a fallacy giving only three choices when additional choices are possible. It leaves out other options, Divine revelation and doctrines of demons. It only offers the three unsatisfactory options. It doesn’t even mention Divine revelation, the only option that actually is rational. It doesn’t even mention doctrines of demons.

One of the mind tricks that some people play with science is to say that they don't deal with truth but only with probabilities. This trick has its roots in the Münchhausen Trilemma. In the Secular Humanist worldview, there are only three possible foundations for thought. None of them are valid, so it impossible to know anything. Therefore, they are not looking for truth, just probability. The problem is that the same foundations for thought that keep them from knowing absolute truth also keep them from knowing probabilities. The must inject arbitrary assumptions, infinite regression, or circular reasoning, so their probabilities are worthless.

You can read more about Agrippa's Trilemma/the Münchhausen Trilemma here.