Our minds and bodies causally interact: our beliefs and intentions cause our bodies to behave in certain ways, and the sensory organs of our bodies cause us to have qualitative experiences and to form beliefs and so on. Let's grant that we can make sense of causation between fundamentally different properties and objects.
But how do we make sense of the fact that my mental states are only ever caused by my bodily states, and vice versa? Why is it that I only ever see the world through my eyes, and only ever behave in accordance with my beliefs and intentions?
physicalism we can say that someone's mind causally interacts with only their
body because their mental states reduce to or are
constituted of their brain states, and only that persons brain states
can interact with their bodily states.
But on dualism there seems to be no explanation.
Therefore, physicalism bests explains the interaction between minds and bodies.