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Tuesday, 20 May 2014 21:37

Dualism Featured

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Leibniz’s law

Leibniz’s law is a law that state that if two objects are identical, then they must have identical properties. Most of the arguments in favor of dualism tend to show that the mind has some properties which the brain or the body does not have; therefore, the two are different. Leibniz’s law states that no two substances can be exactly the same (Mandik, 2013). This means that if the two substances were the same, then they would not be two separate substances. This is a law that can be expressed in a positive manner as if two things are identical; they have common properties that they share.

This also means that if two things share all their properties in common, that means that they are identical. Leibniz’s law has provided various arguments for dualism and according to dualism, full understanding of mental facts will require different elements than it will do for physical. Dualism argues the distinction of mind and matter through employing Leibniz’s law in which two things are identical only if they share exactly the same qualities (Mandik, 2013). The aim of this paper is to provide a discussion of the arguments of dualism according to Leibniz’s law.


According to this law, if A and B are the same thing, then they should possess all the same properties. In case, A and B have different properties they cannot be considered as the same thing. If B has some properties that A does not have, it is right to conclude that A and B are not the same thing (Mandik, 2013). An example that can be used to explain this law is, when looking outside the window and see superman flying by, we might wonder whom the superman is. As the superman is flying outside the window, we see James standing behind us. Reasoning in this situation can be.

  1. The superman is flying outside the window
  2. James is not flying outside the window but standing beside us
  3. Therefore, superman has a property which James does not have
  4. Therefore, superman is not James.

This is an argument that makes sense, and it is according to Leibniz’s law. This is because the superman has a property that James does not have and this can be concluded that James is not the superman. An example of Leibniz’s law argument for dualism is from disembodied existence. In a situation like my mind can exist separate from physical thing and no physical part of me can exist from anything  physical, then according to the law, my mind is not a physical part of me. In this situation, people can imagine that they can exist apart from anything physical. The first part of the statement appears to be right, but there is no way we can float off outside our bodies and if this can happen, then we would not have physical bodies. Stating that my mind is not a physical part of me means that there is a property in the mind which does not share with anything physical.

There are philosophers who have tried using Leibniz’s law when arguing for dualism in different ways. The philosophers have come up with some property which our minds have but the bodies and the brain do not have and vice versa. Through the use of this law, it has enabled them to show that the mind cannot be the same thing as the body or the brain. An example of the argument tends to use the property of being divisible. The body and the brain can be divided to smaller parts whereby it is then argued that the mind cannot be divided into small parts. This means that the mind cannot be the same thing as the body or the brain. An example of another argument that has been used is to show that if my brain weighs 5 pounds, my mind does not weight 5 pounds; therefore my mind and brain are two different things.

The arguments according to Leibniz’s law tend to be employed in almost everyday reasoning. A situation that can be used in everyday experience is like when imagining a situation where a person meets a strange old lady in the street. You might think that the lady is probably Ms Jane who is your neighbor in the next door. The person might ask if Ms Jane is tall and lean and you know that Ms Jane is not exactly tall or lean. This means that the lady by the street was not Ms Jane as the lady in the street was tall and lean. The right argument in this situation is that the lady in the street was lean, and Ms Jane is not lean; therefore, the lady in the street is not Ms Jane. This is an excellent reasoning, and this argument makes at least implicitly of the use of Leibniz’s law.

Problems with the argument

The arguments for dualism tend to share a common flaw as they assume that due to the fact that some aspects of the mental state such as truth, intentionality, privacy, and meaning cannot be attributed to physical substances, they should be attributed to nonphysical substances. Failure to understanding how these properties are generated by the central nervous system will result to not having a clear understanding of how they are produced by the mind. The problem with these arguments is that dualist cannot be able to explain the mechanism in which the souls generate meaning, intentionality, truth, and self awareness (Mandik, 2013).

Therefore, dualism tends to create no explanatory advantage. Because of this, we can use the Ockham’s razor in shaving off the spiritual substance as we ought not to multiply entities more that what is needed to explain the phenomena. Without having Descartes’ prodigious doubt, there is no reason not to believe that bodies do exist. If the only reason that exist supposing that nonphysical minds exists are phenomenal of privacy, and the rest, then dualism tend to unnecessarily complicate the metaphysics of personhood.

Another problem with the arguments is that dualist tends to argue that there is no need to attribute body characteristics to mind because doing this commits the category mistake (Mandik, 2013). For instance, it is right to ask where the hypothalamus is, but it is not right to ask where my beliefs are. This means that it is right to ask how much the brain weighs, but not how much the mind weighs. It is stated that the mind is not something that has size, weight, location, shape, motion, and many other attributes ascribed by Descartes. In case this claim is right, then some of the arguments by Leibniz’s law for dualism are not vulnerable to the examples given.


Mandik, P (2013). This is philosophy of mind John Wiley & Son

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