I go on to handle some objections that have come up in personal debates. The most common of these is that ‘the brain is like a computer and the images in the brain are like those projected on a computer screen’. I encounter this frequently when debating with ‘new atheists’.
Objection: mental images are exactly like images projected on a computer screen. Your brain stores the data and your mind sees the images when that data is accessed.
The image that appears on the screen of your phone or computer right now, here in front of you, is composed of physical events and chemical events from top to bottom:
1. The memory storage is made of protons, electrons, and neutrons.
2. It sends electrical signals through a physical medium to the video chip or chips.
3. From there, an electrical signal is sent through a physical medium to the screen.
4. The screen’s pixels emit photons in a specific pattern based on a series of on-off commands.
5. These photons are absorbed by the rods and cones your eyes, which are also made of particles.
These can all be measured in a lab. They can be independently observed by anyone who looks through the appropriate measuring or observational device. The memory storage device, video chips, wires, electrical currents, photons and so forth are made of particles and physical forces.
The apple-image in your mind is not findable anywhere in physical reality, at all. It can not be independently observed in any lab on the planet, using any type of device whatsoever. Even though it occurs at the same time as the movement of electrons, glucose, and so forth in your head, the image itself is not made of any particles or physical forces. If it were, we could find them, and they would have all the ordinary properties of matter: mass, velocity, spatial extension, and so on. There is no equivalence between the actual image of an apple appearing on a computer screen and actual apple-image appearing in your mind. The digital image is entirely composed of physical particles and the mental image is not.
This analysis of the image, rather than the mind itself, is quite useful because the properties of the mind are quite subtle: knowingness, luminosity, and clarity. These aren’t immediately apprehendable to direct experience. However, they can be discerned from the analysis of the apple-image. The phenomenon which is aware of or cognises (knowing) the apple-image also gives rise to the apple-image (luminosity). Upon inspection, the phenomenon giving rise to the apple is like the apple itself: it does not have any physical properties (clarity). So, this kind of analysis can be quite helpful.