“Really, the fundamental, ultimate mystery – the only thing you need to know to understand the deepest metaphysical secrets – is this: that for every outside there is an inside and for every inside there is an outside, and although they are different, they go together.”
This form of thinking falls under the category known as dialectical monism. Monism is the belief that everything is made up of one fundamental substance. In contrast, dualism is the idea that mind and body are fundamentally different things that interact with each other.
Dialectical monism sort of blends the two in a way. While it believes everything is one substance, it believes this substance to be expressed in two ways such as male and female or in the quote by Alan Watt, “an inside for every outside.”
This is a fundamental question for philosophy and psychology. Moreover, it is an important question for whoever is reading this.