Can an argument be valid and sound if some of its premises are opinion(s)?

I'm doing a first year course in philosophy and I am having trouble understanding if opinions as premises can make a valid argument.

Also, in reference to this, is the premises below considered an opinion:

The conclusion is “we must get into the shelter”. The premises are:

  1. every sentence about the future is right now either true or false
  2. either I’m going to get hurt in this air raid or not
  3. what happens depends on what you do (i.e. getting hurt or not)
  4. The best way to survive and not be hurt is to be in the shelter, whether you like being in there or not
  • 1
    Truth of the premises is moot as far as validity is concerned. The origin of the premises, such as whether they are opinions, articles of faith or random guesses, is also moot as far as soundness is concerned. It only matters whether they happen to be true or false, see IEP, Validity and Soundness.
    – Conifold
    Commented Jul 6, 2020 at 9:37

1 Answer 1


To answer your initial question first: an argument can be valid if its premises are merely opinions, or even if they are false. An argument is conventionally said to be sound if it is valid and its premises are true, so an argument with premises that are merely a matter of opinion has a soundness that is merely a matter of opinion. "Chocolate always tastes better than vanilla, therefore this chocolate ice cream will taste better than that vanilla one" is valid, but its soundness will depend on whether you share the opinion expressed by the premise.

As to the argument you give, there are at least two problems with it. The first premise is highly contentious. It relates to the issue called future contingents, and philosophers have been arguing about this at least since Aristotle. There is an article about it in the Stanfard Encyclopedia of Philosophy. It is not uncommon to hold that statements about the future are neither true nor false until they actually happen, in which case one would say that premise 1 is false.

The other problem is that the argument makes a modal jump from premises that are expressed indicatively as statements of fact, to a conclusion about what we 'must' do. To move from what is true to what must be true is also highly contentious and is arguably simply invalid without additional assumptions. In general, making decisions like whether to get into an air raid shelter may depend on many different considerations, including the probability and impact of the various possible outcomes, and also what alternative actions are open to you and whether these have a priority claim over avoiding getting hurt.

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