Craziness and Irrationality
Craziness and irrationality are both terms used to describe inexplicable things. When someone is afraid of something most consider to be cute, such as rabbits, their fear is considered to be irrational. The problem with such terminology is that it implies that there is not in fact a reason for everything. Which is fine if you don't believe in a reason for everything. However, I believe otherwise.
It’s certainly fair to use crazy in the sense that someone is unpredictable, but most people use the term as to meaning that one is acting without cause. Irrationality is another term that implies reasonlessness for it is defined as being ‘not in accordance with reason.’ For something not be in accordance with reason is to say that something is without reason. Whereas crazy can be supplanted with unpredictability, I believe irrationality needs a revamped definition. People often use the term when someone is making arguments outside the realm of said person’s range of understanding. So a better terminology for irrationality would be 'not in accordance with the realms of reason pertaining to the relevant boundries of the discussion' or, 'outside the realm of one's understanding.'
In conclusion, craziness, insanity and irrationality all generally hint at a lack of reason, but determinism entails that in the grand scheme of things there is a reason for everything. Claims pertaining to craziness and irrationality, from a deterministic view point, are basically claims of incomprehension .