«فَإِنَّ الْأَوَّلَ هُوَ الَّذِي يَكُونُ سَابِقًا عَلَى الْغَيْرِ»
The former is what stands prior to the other.
The discussion distinguishes certain relations by asking which conception is prior and how the second is evoked relative to it. There is no single fixed order for every comparison; the relevant conception and its relation determine the sequence.
In one context 'height' may call up 'depth,' while another begins with depth. The mental order of association is not necessarily the same as universal chronological priority.