This concept is difficult.

His poetry is esoteric, difficult for the general public to understand.

I am amazed at the immeasurableness of his thoughts.

His irresponsible behavior caused an accident.

We started a discussion about an important issue.

We discussed the issue.

This plan includes unlimited data.

He is majoring in philosophy.

In philosophy, the concept of infinity provokes very profound discussions.

I was amazed at his extraordinary talent.