It’s easy to confuse these two concepts so I wanted to give a brief differentiation. I’ve noticed the confusion on the blog here, and I’ve had two students attempt to construct an argument for determinism when they were actually arguing for fatalism. Determinism entails that an event is necessarily constrained to actualization by causal relations. Fatalism entails that an event is necessarily constrained to actualization, but it is not by causal relations. This becomes an issue with simple foreknowledge (i.e. If God foreknows any state of affairs then those state of affairs happen necessarily. So, if God foreknows I will be sitting down at t1 do I have the freedom to stand up at t1?).
Determinism (let S be a state of affairs)
S1 → S2 → S3 → S4
Let this represent a causal relationship between each state of affairs. So if I were to ask the question, “If God foreknows that I will be sitting down at S4 do I have the freedom to stand up at S4?” The answer is no. I don’t have the freedom to stand up because in each I was determined to sit down by the prior causes and God foreknows what will happen because the causes logically precede God’s foreknowledge (in the case of natural knowledge) or are concurrent within God’s foreknowledge (though this would deny all possible worlds except for one, the actual world).
S1ʹ → S2ʹ → S3ʹ → S4ʹ
In the above states of affairs, there doesn’t need to be any direct causal relationship (so let’s use prime to differentiate). Now let’s ask the above question concerning God’s foreknowledge and the necessary actualization of any state of affairs.
God foreknows S4ʹ will happen: Because S4ʹ will happen (by virtue of God knowing that it will happen), S1ʹ → S2ʹ → S3ʹ must necessarily happen to bring about S4ʹ. Remember, any prior states of affairs happen necessarily as well by virtue of God’s simple foreknowledge. This is different from determinism because the states of affairs are not [necessarily] causally determined or related to each other.
Determinism and fatalism both have their problems. I find determinism to be problematic because of the problem of evil and human freedom. Fatalism confuses the logical moments of God’s knowledge. So the question I’ve been asking is simply just a bad question. I’m taking God’s free knowledge and putting that logically prior to God’s natural knowledge or middle knowledge (depending on what I’m objecting to). So if I’m going to ask if I can (natural knowledge) do anything other than what God foreknows (free knowledge), then I’m making the third moment precede the first moment. It’s simply incoherent and inconsistent.