Johann Friedrich Herbart (1776-1841) likened ideas to Leibniz's monads by saying that they had energy and a consciousness of their own.
Likewise, according to Herbart, ideas strive for consciousness. Those ideas compatible with a person's apperceptive mass are given conscious expression, whereas those that are not remain below the limen in the unconscious mind. Herbart is considered to be one of the first Mathematical and Educational psychologists.