Outward judgment: Public and legal dealings depend on reliable words and acts.
Inward reality: Ultimate knowledge of sincerity, conviction, and hypocrisy belongs to Allah.
Judgment of actions: Whether an act occurred, how serious it was, and whether a doctrine was denied are separate inquiries.
Thus a believer's weakness does not itself justify claiming certain knowledge of inward rejection. Conversely, an uttered formula does not give other people absolute access to inner sincerity.
This distinction protects both the functioning of outward religious law and the limits of human knowledge about hidden hearts.