I am a necessitarian, meaning, I believe that the only thing that is possible is what actually happens. The reason for that is because I don't believe any possible world except this one exists. However, I still believe in a weak notion of possibility. I believe that a set of sentences S is possible in the logical sense if no contradiction can be formally deduced from S. This does not conflict with my necessitarianism, or so I think, because I believe there is in fact no possible world other than this one, so S is merely possible in a very weak sense. But what is the truth of the matter? Can a necessitarian consistently believe in this weak notion of possibility? And what have philosophers written on this topic?

  • "Being a necessitarian" is like "being a critic", you have to finish the phrase for it to have a meaning. A critic of what, necessitarian about what? There are multiple kinds of necessity, logical, physical, metaphysical, biological, practical, nomic, etc., so a necessitarian about one may well be a possibilist about others. Each kind has its own collection of possible worlds.
    – Conifold
    Commented Apr 12 at 22:50
  • This is a nit-pick, but ‘merely possible’ is jargon for something that has, but only has possible existence in possible worlds other than our own. For example, unicorns seem to be possible but not actual, i.e. merely possible.
    – PW_246
    Commented Apr 13 at 0:23

1 Answer 1


If you believe that possible futures don't exist, there is only one actual necessary future, your belief must also be necessitated. Right?

How is this possible? A belief implies uncertainty about truth, a doubt. How can uncertainty be necessitated?

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