How do we describe a "sophisticated person"?
I don't think there is an exact Chinese counterpart for 'sophisticated'. It depends on the context. 

世故 (worldly) is the context-agnostic translation but sometimes it has a negative connotation of slyness. When you use it on a 10-year old, it's almost surely negative.

Like the other comment mentioned, (少年)老成 can be used when to say a kid is sophisticated, but 老成 also implies '(psychologically) mature'.

The options Google translation gave you (复杂/尖端/诡辩) are definitely not the common words one would use to say 'sophisticated'. They may serve the purpose only in very specific contexts.

Edit:

For the example you've added to the question, I'd choose 深邃 (deep) which is more idiomatic  than the other words mentioned above to praise a philosopher's thinking ability. 


  虽然年轻稚嫩，可是他的思想比世界上最伟大的哲学家还要深邃。


超前 (ahead of time/peers/age/...) mentioned in the other answer, or 领先 (in the lead) is also fine to use, though the meaning is slightly different: 超前/领先 is describing the thoughts, the outcome of thinking, rather than the thinking ability.