He goes on to note that the ego is essentially a system of perception, so it must be closely related to the preconscious (27). Thus, two primary components of ego are a system of perception and a set of unconscious (specifically, preconscious) ideas. Its relationship to the unconscious id (), therefore, is a close one. The ego merges into the id (28). He compares the dynamic to that of a rider and a horse. The ego must control the id, like the rider, but at times, the rider is obliged to guide the horse where it wants to go. Likewise, the "ego must, at times, conform to the desires of the id."