Ignorance, feeling, impulse and perception--all are instinctive processes. We operate a radar system which senses our territory. Yet we cannot establish ego properly without intellect, without the ability to conceptualize and name. Since we have so many things happening, we begin to categorize them, putting them into certain pigeon-holes, naming them. We make it official, so to speak. So “intellect” or “concept” is the next stage of ego, the fourth skandha, but even this is not quite enough. We need a very active and efficient mechanism to keep the instinctive and intellectual processes of ego coordinated. That is the last development of ego, the fifth skandha, “consciousness.”