Do You See What I See?
Philosophy of Mind came into its most compelling forms during the age of modern philosophy beginning with René Descartes. Perhaps infamously, Descartes claimed that mind and body are two distinct substances – philosophical jargon for what exists without the aid of any other thing. For Descartes, the world was clearly and distinctly physical in one sense and entirely mental in another. This seems perplexing, and Descartes did concede that the mind and body were closely intertwined and appeared to act with respect to one another, but his arguments clearly press that they are not causally connected in any way. These notions of dualism seem nearly preposterous with the advent of modern science, but were nonetheless important in developing our thought about the mind in the modern era.
Dualism gave rise to other interesting, yet now strongly refuted movements. One of these was idealism, or the doctrine argued famously by George Berkeley that states that all that exists are either ‘ideas’ or minds that perceive them. In this sense, an idea is defined as that which is perceived, inclusive of information imprinted on the senses, passions and operations of the mind, and conceptions formed by imagination and memory. Importantly, Berkeley argues that these ideas exist ‘in the mind’ exclusively: that is, they are purely mental and all things are simply combinations and aggregations of ideas. These immaterial ‘ideas’ then, are the only objects of human knowledge under idealism, and this theory denies the existence of physical objects entirely! The notion seems preposterous, but there is a very interesting argument found within idealism that can throw our conception of perception for quite the proverbial loop.
One of the main arguments against idealism is the apparent true existence of material objects in the external world. Modern science has allowed us to know with a degree of certainty that we exist in a world that contains physical entities separate from our mental space. Bertrand Russsel, a physicalist, famously made such arguments for the existence of the material world. He coined the term ‘sense data’ to refer to that which we perceive from objects in the environment, e.g. the light rays reflecting off of them. In his thinking, this sense data is caused by an actual material object in the external world, thus endorsing the existence of physical objects. This certainly seems more plausible than idealism given our current level of understanding about the physical world. However, the idealist refute of physicalism draws on an idea called perceptual relativity that is interesting in itself and worth knowing about.
Perceptual relativity works similarly to the theory of relativity from physics, but applies it to perceptual content, and it is with this crafty syllogism that an idealist can argue that nothing really exists outside our own minds and ideas. If the idealist accepts that the objects perceived are ideas that exist only within the mind of the perceiver and those things are made up of more ideas which also only exist in the mind of the perceiver, it follows that each perceiver apprehends a different object entirely, rather than a different affection of the same object as a consequence of having different points of view. In other words, each person looking at a common object perceives an entirely unique object, just as if they were looking at two completely different things, e.g. a house and a boat. This seems absurd, but it is nonetheless effective for arguing the physical world out of existence. Taking ideas as exclusively mental phenomena, it remains logically valid to argue that each person perceives a different idea when looking at the same object in that different angles or in different levels of light and shadow make the object of each person’s perception unique to them alone.
While the argument from perceptual relativity is interesting, it remains completely absurd in our modern context. Given that we can forcefully argue for the existence of the material world down to the level of molecules, atoms and subatomic particles that (perhaps) move faster than the speed of light, the idealist well seems to have run dry. It seems evident, if not universally true, that there is an external world filled with a variety of physical objects that exist in a space outside our minds. We may have thoughts of said objects and file them into our minds, but it by no means follows from this that an object solely exists in our minds and is not like the ideas of others about the same object. However, the flip side of this comfortable position would make an assertion about material objects themselves. What are they really made of? On a deep level, they are simply electricity – energetically favorable collisions of packets of energy that are perceived by our sense organs and constructed into a nice, organized stream of consciousness by our brains. To get even loftier, we’ve developed quite a system to differentiate all the different types of electricity out there by giving them names like tree, book or cheeseburger. These are really just ideas about the various clouds of electricity we interact with every day, so how far from idealism have we really come? Are our ideas about voltage simply existing within our own minds as a function of the information our brain is wiling to let us perceive?
Treatise Concerning Human Knowledge – George Berkeley
The Problems Of Philosophy – Bertrand Russell