Nihilism is a form of failed seriousness rather than its opposite.

Evidence

Conscious of being unable to be anything, man then decides to be nothing. We shall call this attitude nihilistic. The nihilist is close to the spirit of seriousness, for instead of realizing his negativity as a living movement, he conceives his annihilation in a substantial way. He wants to be nothing, and this nothing that he dreams of is still another sort of being, the exact Hegelian antithesis of being, a stationary datum. Nihilism is disappointed seriousness which has turned back upon itself. — Simone de Beauvoir, The Ethics of Ambiguity, 50

Categorization

• DEFINE: Core typology insight: the nihilist still treats ‘nothing’ as a thing — a stationary being — so he never escapes the serious structure; crucial for the reader’s goal of sorting real people into the types.
• XREF: Rhymes with Nietzsche’s ‘active nihilism’ and with the reader’s earlier note that the serious man’s flight from freedom is the common thread across sub-man, serious, and nihilist.