The insanity of logic is harder to detect because it if often used to propel a temporal belief. However, as the statement implies, because the belief is temporal and can be manipulated by humanity, the support of it will lead to insanity. I.e. because we logically trust in something that we can change, we have to trust in ourselves but we inherently know that we are untrustworthy.

However, I would argue that artist are also very prone to insanity, for the same reason. If an artist finds a temporal abstract as his inspiration (physical appearance based love, self fulfilling emotionalism), his sanity is no more stable than a mathematician trying to describe the direction and rate of travel of the universe. As a person who bases everything in logic, the artist is trying to create something eternal from something temporal. In either case, what is created is still subject to the will of what created it which is again, inherently imperfect.

The key to the statement though is where it says "The last thing that can be said of a lunatic is that his actions are causeless." This is the true distinction between sanity and insanity. Insanity fights for a cause which can be manipulated and is temporal by nature. As such, there is no trust or assurance in it. The sane fight for a cause which is by nature eternal and can not be manipulated. All the sane can do is describe the cause and not define it.

No matter the mind orientation of a person (artistic or logical), the state of the person's sanity is dependent on the basis of their inspiration or reasoning, not on their God determined mindset.