Are there any cogent arguments
against selfishness?

Ambiguous words

Most thinkers and writers do not provide a glossary of well-defined terms, terms that could have ambiguous meanings.

The meaning of "selfish"

As such, the reader is often left guessing (or assuming) the denotation of ambiguous words that a given author or speaker is using. I often find myself guessing about the meaning that an author intends when using the ambiguous word “selfish.” When I use this word, I simply mean, “concern for one’s self-interest.” This definition does not imply that you are not concerned also about the self-interests of others. Additionally, it says nothing about whether or not the self-interest is short-term or long-term, which may be conflicting.

People argue against short-term selfishness,

favoring long-term selfishness

Considering all this, I have read many polemics that argued against “selfishness.” In every case, what the author was arguing against was short-term selfishness because it damaged or interfered with long-term selfishness. The writer was, in fact, favoring selfishness, as long as it included long-term selfishness.

In conclusion, I have found no cogent argument against selfishness, given the meaning, “concern with one’s self-interest, both long-term and short-term”.