Is determinism rational? Since there is no evidence to prove/disprove the existence of 'fate', is it rational to have a determinist point of view? Or is there evidence and I am merely ignorant on the subject?

Determinism is the thesis that a complete description of the universe at one time and the laws of nature logically entails a complete description of the universe at any later time. Though this definition does not talk about causation, determinism is also often understood to mean that every event in the universe is completely caused by a set of prior events, in accord with the laws of nature. I don't think this definition of determinism should be equated with 'fate' since fate suggests that certain things are going to happen no matter what anyone does and perhaps also that some power, such as God or gods or the Greek Fates, has control over fate (and hence what happens to you)--so, Oedipus was fated to sleep with his mother, no matter what he tried to do to avoid that fate and it looks like the gods imposed that fate upon him. Determinism, on the contrary, does not entail that certain things will happen no matter what. On the contrary, it suggests that what happens on the future depends on what happens in the present, including human actions--i.e., future events would happen differently than they actually do if earlier events had been different. And determinism does not entail that any power is in control of what happens (nature and the laws of nature are not controlling things if we assume that control requires an agent who aims to bring about certain ends). Finally, determinism is not, by definition, the opposite of free will. Indeed, most philosophers think that determinism is compatible with free will.

OK, so do we have reason to believe determinism is true? Probably not. The most prominent interpretation (Copenhagen) of quantum physics suggests that micro-physics is indeterministic. That is, certain events are not logically entailed by or sufficiently caused by prior events; rather, given the exact same causal conditions (e.g., as an electron hits a barrier) and the laws of physics, there is an objective probability that more than one outcome (effect) will occur (e.g., 50% that the electron will penetrate the barrier and 50% that it will be reflected). Nothing determines or causes which of those events occurs (though prior events cause that one of the events will occur). Some, however, think quantum physics can be interpreted in a deterministic way (Bohmian interpretation). And some think that even if the micro-level is indeterministic, the macro-level including human behavior, is deterministic. (I think that view is implausible since quantum events likely 'percolate' up to have some macro effects, perhaps in chaotic systems in which large differences can be produced by small differences.) So, the evidence is not in. Some philosophers think determinism cannot be proven or disproven, but I don't think we should assume that.

If part of what you were asking is whether a belief in determinism is somehow self-contradictory, and hence irrational, I think the answer is a resounding no.

Read another response by Eddy Nahmias
Read another response about Freedom