[1] This coordination of mental and bodily events has been postulated to occur either in advance by means of God (as per Gottfried Leibniz's idea of pre-established harmony) or at the time of the event (as in the occasionalism of Nicolas Malebranche) or, finally, according to Baruch Spinoza's Ethics, mind and matter are two of infinite attributes of the only Substance-God, which go as one without interacting with each other.
Psychophysical parallelism is a third possible alternative regarding the relation between mind and body, between interaction (e.g., Mind–body dualism) and one-way body-to-mind causality (e.g., materialism, epiphenomenalism).
"[3] Psychophysical parallelism can be compared to epiphenomenalism due to the fact that they are both non-fundamentalist methods to link mind and body causality.
However, from the perspective of epiphenomenalism, the mental states of pain would be occasioned by the physical event of the neural reaction of cutting through the skin.
Causal closure iterating that the physical and mental world cannot interact presents an obvious issue in regard to dualism.
In the world of dualism, the mind and body are two entirely separate constituents which continuously interact with each other, in order for the human being to function as a whole.
This theory offers an explanation on behalf of dualism : the mind and body remain two distinct properties of humans, yet they do not interact with each other.
For example, if the body is injured, God is aware of the injury and makes the mind, or the person (subject of experience), feel pain.
Since everything that exists is a modus of God, Spinoza's concept represents a monist account of parallelism, contrary to Leibniz's pluralist version.
German philosopher Gottfried Wilhelm Leibniz concluded that the world was composed of an infinite number of life units called monads (from the Greek monas, meaning "single").
However, humans possess many types of monads, varying from very simple to very complex forms, which explains why the ideas we experience at times differ in clarity.