«الْجَامِعُ بَيْنَ الْجُمْلَتَيْنِ إِمَّا عَقْلِيٌّ»
The link between two things may be rational.
A rational jāmiʿ is a relation through which the intellect finds reason to bring two concepts together in the compositive faculty. It rests on an intelligible conceptual connection, not merely on someone's chance experience of seeing the things together.
The notable patterns include unity of conception, similarity, and correlation or relational pairing. They must be distinguished instead of being treated as interchangeable.