Like Fichte, Brentano had one simple and powerful insight. He declared: there is a basic difference between a mental and physical act. if I slip on the snow and fall flat on my back, that is an unintentional physical act. But there is no such thing as an unintentional mental act. When I think, I have to think about something; I have to focus my mind on it. You could compare all mental acts (thinking, willing, loving, trying to remember something) to a searchlight beam stabbing into the darkness. There is an element of will, of 'intentionality,' in all mental activity. So it is quite inaccurate to compare mental activity to chemistry, or to a kind of drifting, like leaves on a stream. It flows purposefully or not at all.

p. 35 - Rudolf Steiner: The Man and His Vision (1985)