Major philosopher unable to be talked about (4)

I believe the answer is:

kant

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'major philosopher' is the definition.
'Kant' can be an answer for 'philosopher' (Immanuel Kant, 1724-1804). I'm unsure of the 'major' bit.

I don't understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for kant that I've seen before include "Immanuel --, German philosopher" , "Idealist" .)

I've seen this clue in The Irish Times.

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