The judgment of whether lines are parallel depends on conscious mental analysis.

Question: When looking at a line, at first glance it appears non-parallel. Is this non-parallelism discerned by the eye consciousness or by the mind consciousness? Later one feels it is parallel. Is this conflicting mentality that of the mind consciousness, or a conflict between the eye consciousness and the mind consciousness?

Answer: The shape of a pattern belongs to visible form (saṃsthāna-rūpa), which is a mental sense-object (dharma-viṣaya), within the domain of the mind consciousness's discernment. The eye consciousness only sees colors; everything else is the content of the mind consciousness's discrimination. Judging whether something is parallel or not is determined by the mind consciousness through thinking and analysis. When the mind consciousness cannot reach a decisive conclusion in its discernment, conflicting emotions arise, and it becomes unable to make a final determination of whether it is parallel or not.