Determinism, free will and moral responsibility

3 min readJan 28, 2021


This is an excerpt of a larger set of comments on determinism and compatibilism, and serves as a short introduction to the concepts.

Determinism is a philosophical concept stating that, given full information about a paste state, the future is fully determined. That would appear to imply a lack of free will: if the future is determined by the past (as physics generally requires), aren’t one’s decisions set from the start?

That causes serious issues, because moral responsibility requires freedom to act. If the decision and outcome are set from the start — how can you be blamed? It would be like assigning blame to the Sun for causing a draught. More specifically, moral responsibility generally requires three (or perhaps four, if you consider awareness of the causal link and of the moral aspects of the consequences thereof as separate) aspects:

  • A causal relation (person P, through action A, caused event E).
  • Awareness of the consequences (P knew A would result in E, and is aware that E is immoral).
  • Freedom of choice (P willingly performed A, and could have done differently).

Clearly, without freedom of choice, it is difficult to assign moral responsibility. Compatibilism aims to unite these two seemingly opposed concepts.

To go further into detail, we can consider two main ways of considering the effect of determinism on free will. The first considers alternate possibilities. This can be formally stated as:

  1. If a person acts of their own free will, it is possible for them to have acted otherwise.
  2. If determinism is true, nobody can act different than they actually did.
  3. Hence, if determinism is true, nobody can act of their own free will.

All rather straight-forward. However, there is a more interesting view for this, namely sourcehood. In abstract terms, we can consider a person performing an action. If determinism is accurate, then there is a huge chain of events connecting the past with the current action.

Let’s consider an example. If you are hungry, what caused that? Well, quite plainly; you haven’t eaten in some time, or perhaps performed strenuous exercise. Then, what caused you to avoid eating? A lack of time due to university, maybe. What resulted in you going to university? Likely, parental expectations coupled with intelligence. What caused those parental expectations? Culture, their parents, monetary considerations — a myriad of connecting causes.

Coincidentally, this is strongly related to a fascinating aspect of epistemology, or the philosophy behind knowledge. Taking a common requirement, the principle of sufficient reason— which can be summarized as everything requiring an underlying cause — we immediately run into trouble.

Either we have an infinite series of causes, so ABC→D ad infinitum. Or we halt at some particular point: A→B→C. Can we truly back up just why we stop at C, and no longer demand an explanation? Finally, we can move to circular logic, so a structure of A→B→C→A. In common terms, this is a chicken-or-the-egg case.

These three options comprise the Münchhausen trilemma, which has resulted in three philosophical views, respectively:

  • Infinitism
  • Foundationalism
  • Coherentism

These are all fascinating and highly detailed fields of study — on which I am currently still working.

After a sizeable detour, we can return to the original point. The source of the feeling of hunger, and the resulting action of eating, is not inside the agent, but emerged through causes entirely unrelated to it. Then, free will can only exist if the person is the ultimate source of the action. Summarizing this:

  1. A person acts of their free will if they are the ultimate source of their actions.
  2. If determinism is true, no person is the ultimate source of their actions.
  3. Therefore, if determinism is true, no person acts of their own free will.

These two options lead to fascinating perspectives on how to avoid or sidestep the issues posed by determinism. I recently read H.G. Frankfurt’s Alternate Possibilities and Moral Responsibility, published in 1969 in The Journal of Philosophy (Vol. 66, No. 23, 829–839). This short comment should serve as a quick refresher on the concepts of determinism and free will, since the concept of alternate possibilities is central to Frankfurt’s thesis in the paper.