يَتَجَلَّى بِهَا الْمَذْكُورُ
The matter becomes clear through that attribute.
Tajallī cannot be restricted to visual appearance. Hearing a sound, understanding a mathematical relation, and apprehending the impossibility of a contradiction are different kinds of cognition. In each case, something becomes intelligible in a determinate respect.
Thus an object of knowledge need not be a colored or shaped body. Sensible particulars can be known through perception, while conceptual relationships and judgments can be known intellectually. The manifestation of an object to understanding is broader than its appearance before the eye.