Posted by Ali Reda | Posted in | Posted on 5/13/2015

Dualism, is the view that that there are two separate and distinct substances that make up a human being: mind and body. In religious terms, the mind is sometimes equated with the soul.

Monism, because it describes a belief in one substance, can be used in two distinct ways:

To describe the view that only matter, or the physical body, exist (materialism).
To describe the view that only mind, or spirit, exist (idealism).

Platonic Dualism

Aristotle shared Plato's view of multiple souls and further elaborated a hierarchical arrangement, corresponding to the distinctive functions of plants, animals and people: a nutritive soul of growth and metabolism, that all three share; a perceptive soul of pain, pleasure and desire, that only people and other animals share; and the faculty of reason, that is unique to people only. In this view, a soul is the hylomorphic form of a living organism. Thus, for Aristotle, all three souls perish when the living organism dies. For Plato however, the soul was not dependent on the physical body; he believed in metempsychosis, the migration of the soul to a new physical body

Substance Dualism

Descartes concluded that the mind was a completely distinct substance from matter because:

  1. Matter is measurable, has dimensions, can be sensed, divided, destroyed and altered. Mind, however, can almost be defined as the opposite of this, it is invisible, without dimensions, immaterial, unchanging, indivisible and without limit.
  2. Descartes cannot doubt the existence of his mind, but can doubt the existence of his body. Since what I cannot doubt cannot be identical to what I can doubt (by Leibniz's Law), mind and body are not identical and dualism is established.

Descartes’ response was to suggest that the two substances meet in a part of the brain called the pineal gland. His reasons for choosing this seem to have been that the gland in central (unlike the other parts of the brain which are bilateral – mirrored on each side) and that it does not occur in animals. This latter fact was understood by Descartes as relating to the presence of a soul in humans and not in animals, whom he considered mere machines. However, modern research has also found a similar gland in mammals and lower vertebrates.


  1. How can conscious experiences like your pain exist in a world that is entirely composed of physical particles and how can some physical particles, presumably in your brain cause the mental experiences? (This is called the “mind-body problem.”).
  2. How can the subjective, insubstantial, nonphysical mental states of consciousness ever cause anything in the physical world? How can your intention, not a part of the physical world, ever cause the movement of your arm? (This is called the “problem of mental causation.”) 
  3. No one has ever succeeded in giving an intelligible account of the relationships between these two realms.
  4. Argument from brain damage, in instances of some sort of brain damage, it is always the case that the mental substance and/or properties of the person are significantly changed or compromised. If the mind were a completely separate substance from the brain, how could it be possible that every single time the brain is injured, the mind is also injured? Indeed, it is very frequently the case that one can even predict and explain the kind of mental or psychological deterioration or change that human beings will undergo when specific parts of their brains are damaged.
The correlation and dependence argument against dualism begins by noting that there are clear correlations between certain mental events and neural events (say, between pain and a-fiber or c-fiber stimulation). Moreover, as demonstrated in such phenomena as memory loss due to head trauma or wasting disease, the mind and its capacities seem dependent upon neural function. The simplest and best explanation of this dependence and correlation is that mental states and events are neural states and events and that pain just is c-fiber stimulation.

Searle says:
Notice that these arguments still leave dualism as a logical possibility. It is a logical possibility, though I think extremely unlikely, that when our bodies are destroyed, our souls will go marching on. I have not tried to show that this is an impossibility (indeed, I wish it were true), but rather that it is inconsistent with just about everything else we know about how the universe works and therefore it is irrational to believe in it.


Following Descartes’ death, some philosophers – such as the Frenchman, Nicholas Malebranche (1638 – 1715) – recognised this problem and tried to address it whilst still holding to the dualist view. Malebranche’s suggestion was that neither body nor mind were causally related, but were in fact connected by divine interaction. So, whenever we wish to lift an arm, for instance, God must intervene to cause the body to obey (similarly, whenever the body feels pain, God must cause that sensation to occur in the mind). But problems arise: if God is responsible for all seeming causal interactions, is he also responsible for evil deeds? This would make him the unwitting agent in murders, crimes, etc.

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