ثم يثبتون أن ما وراء المعنى المشترك غير صالح لاقتضاء الحكم
They then establish that attributes other than the common meaning are unfit to produce the judgment.
The text proposes testing an attribute in another case where the attribute is present but the judgment is absent. Such an observation can demonstrate that the attribute alone is not sufficient for the judgment.
If two things share a feature but only one exhibits the effect, that shared feature by itself provides a poor explanation of the effect.