What does "half-primitive vigor" mean?

Question

In the short story The Planet of the Dead by Clark Ashton Smith, I would like to understand the meaning of "half-primitive vigor":

He had lived as an intellectual sybarite; and by virtue of a half-primitive vigor, had not yet fallen upon the spiritual exhaustion and desolation, the dread implacable ennui of racial senescence, that marked so many of his fellows.

There are several meanings in the dictionary but none make really sense to me with "half".

Answer 1

I'm suprsed that the question was migrated. The use of "half + adjective" is common enough:

"He was half-dead with exhaustion".

"She was half-aware of a conversation taking place in the adjoining room".

"I was half-convinced by the ridiculous argument."

etc.

The meaning of "half" is not literal but more "partly" or "to a lesser degree" or "almost" - the context will decide.

Thus "and by virtue of a half-primitive vigor" = and by virtue of his vigor which comprised a mixture of basic survival instincts common to all people and creatures, as well as more sophisticated techniques learned from his experience, etc.

Answer 2

The comparison here turns on "half-primitive vigor" vs. "racial senescence." A people early in their history (by which is generally meant their appearance in historical records -- a concept more applicable to civilizations, though not strong even there, but unfortunately commonly applied to races in 1932) are bursting with life and can-do vigor. As their history accumulates, the people as a whole age through a maturity and end up in senescence -- decadence being a more direct and less metaphorical term.

Now, the character referred to does not actually have "primitive vigor" -- he does not come from a young, vigorous, energic race. However, through some fluke, he has inherited a half-measure of it (half not being precise here) from his ancestors, and this prevents his sybarite habits from turning him into a case of spiritual exhaustion and desolation,