Yes, one can think of oneself as 'indispensable' if one has learned something else that nobody else knows, but one would be incorrect.
The truly 'indispensable' man is one who who is the extroverted autodidact.
That is, one who learns on their own and then spreads that knowledge about.
Rare birds them.
And you know what 'they' say about autodidacts: "The autodidact is truly the theodidact."
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