The goal of this introductory presentation will be to explore the commonality of different approaches to RFI mitigation, in order to help build intuition on some of the conditions under which interfering signals can be cancelled or subtracted without damaging the celestial signals that radio astronomers strive to receive. Some of the methods can be visualized in much the same way that astronomers treat gain closure information and aperture synthesis. Cancellation of multiply scattered RFI appears at first glance to be a complex problem but can be treated very simply. Adaptive filters applied in the time-domain have precise analogs in the post-correlation frequency domain.