Why can't I return the scene view gizmo to perspective?

I switched the view selection gizmo found in the upper right corner of the scene view out of perspective, and now no matter how I click on it I can't return to a perspective view. My objects show up fine in both the scene and game views, though they don't show up in the camera preview, (probably because of the view gizmo issue). Right clicking pulls up the menu which always shows one of the other views and perspective both selected at the same time. So, what stupid thing am I doing this time?...;^)