Is quoting an authoritative source a useful or effective way to demonstrate that an assertion is correct?
Kenneth T. Gallagher described "all truly philosophical questions" (page 34) from the position of Gabriel Marcel as "mysteries" rather than "problems".
Consider the differences between these words:
A problem, is an inquiry which is set on foot in respect to an object which the self apprehends in an external way. (page 31)
Quoting an authoritative source may be the answer to a problem or question of some object apprehended in an external way. Questions about the validity of symbolic arguments may be examples of such.
A mystery, on the other hand, is a question in which what is given cannot be regarded as detached from the self....A mystery is a question in which I am caught up. (page 32)
If the philosophical musing is a mystery, such as questions about freedom, the authoritative source would be evidence for the person to consider who will then have to understand the musing not as some object "detached from the self" but as a mystery in which "I am caught up".
Consider the question:
Is quoting an authoritative source a useful or effective way to demonstrate that an assertion is sensible, reasonable or wise?
If Gallagher and Marcel are correct and the assertion is not a problem but a mystery, then the authoritative source may be useful but the demonstration that it is sensible, reasonable or wise is up to the person who is "caught up" with that assertion as a mystery.
Kenneth T. Gallagher. The Philosophy of Gabriel Marcel. 1975. Fordham University Press.