The difference is in how the speaker (writer) is choosing to structure the temporal relationships. In many contexts, there is more than one possible choice; sometimes some of the choices are ruled out by objective circumstances, or by other words the speaker is choosing to use.
In this case, the choice of the present perfect (has introduced) would signify that the writer is choosing to convey some present relevance of the introduction. This is unlikely, because Kant died long ago, and would only be appropriate if the writer were conveying that Kant's action was part of a development that is still continuing.
The choice of the past perfect (had introduced) would indicate that the writer was focussing on some particular time in the past, but later than Kant's introduction. It would fit if the writer had already established that they were talking about some such time - perhaps the time of some subsequent development. Alternatively, the use of the past perfect could establish some later temporal focus, which the writer then went on to talk about further.
The simple past (introduced) is neutral, and doesn't have any such implications.
So in isolation, there is no reason to use the past perfect in that passage; but it could fit if it were preceded or followed by material set at some later time.
