Justifying claims

Question

Many posters report claims in statements such as

• This author claims that…
• Some claim that… OR Someone claims that…
• I read that…

containing no supporting evidence, source or reference.

Should we insist that claims always be supported in the body of post (question or answer) by a source citation?

Should we create a comment template requesting that sources be indictated?

Answer 1

I think that such reported claims should be judged case by case. There are completely different scenarios connected to claims.

For example

1. "my teacher claims that blackbody entropy is proportional to the surface and not to the volume";
2. "in a book, J.Smith claims that we can get energy from the orbital motion of asteroids";
3. "I read somewhere, that Newton used the concept of energy";
4. "I recently read that Swendsen claims that the $\frac{1}{N!}$ factor in front of the canonical partition function has nothing to do with the indistinguishability of particles";

For different reasons, I do not think it is reasonable or important to ask for a source citation for the examples from $1$ to $3$. In the case of $1$, the original claim is not verifiable but this does not hamper the possibility of an answer addressing the underlying concepts independently of the context where the question originated. In the case n. $2$, it would probably be wise to ask for clarifying the question, independently of the exact title of the book. Answer to question $3$, even without references, should be simple to answer for everybody who knows that energy was formally identified and used almost a century after the Principia. In my opinion, the only case where a specific source for the claim would be required is n. $4$. However, if a reference to Swendsen's papers where the problem is addressed would be made in an answer, that would be ok.