While current approaches for the ablation of atrial fibrillation are often effective, they are only partially rooted in mechanistic understanding.  Accordingly, they are unable to identify which patients will or will not do well after a single procedure, and which lesions sets should or should not be performed.  Mechanistic thinking in AF falls into one of 2 dominant schools of thought – the first proposing disorganized activity that self-sustains with no ‘driver’, and the second describing drivers that cause secondary disorganization. This dichotomy has come to a head in the setting of a plateauing of ablation success and greater demand for efficacious intervention to treat AF by patients and funding agencies. Differences in mapping may explain these schools of thought, with proponents of the disorganized hypothesis studying small atrial areas at high resolution, and proponents of the driver model studying wide fields-of-view at sometimes lower resolution.  Focal impulse and rotor modulation (FIRM) mapping combines wide field of view with novel physiologically based signal filtering and phase analysis, and has revealed that human AF is often sustained by rotors and focal sources.  In the CONFIRM Trial, targeting stable AF rotors/sources for ablation improved the single-procedure efficacy for paroxysmal and persistent AF over conventional ablation alone, as confirmed by independent laboratories.  FIRM gives a theoretical foundation to explain why certain lesion sets are effective in a given patient, by intersecting AF sources in patient-specific locations.  FIRM also explains why even extensive ablation may be ineffective, by missing AF sources particularly in the right atrium.  These insights have reinvigorated interest in the physiology of human AF, and rotors with varying characteristics have now been identified by many groups.  Rationalizing these findings will help catalyze the understanding AF substrates, and translate into even better therapy for our AF patients.