If such a furious trope may stand, his special lunacy stormed his general sanity, and carried it, and turned all its concentred cannon upon its own mad mark; so that far from having lost his strength, ahab, to that one end, did now possess a thousand fold more potency than ever he had sanely brought to bear upon any one reasonable object. what is the meaning of this excerpt?

Ahab has lost his sanity but is still determined to have his revenge.

Explanation:

The meaning of this excerpt is that Ahab has become totally crazy but this craziness fuels him to seek revenge. Inevitably,He has reached a point where he is as much a victim as he is an aggressor. The whale  is   the target of his fury and  his mind is lost in the  lunacy of  his pursuit for  revenge.  He has reached a point of no return.

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