Theophilus asked:

What is the difference between real and perceived space?

Answer by Jürgen Lawrenz

This depends on what you mean by ‘space’. Are you speaking of a ‘logical space’, or the ‘space between 2 words’, or ‘outer space’ etc.?

You see, your question is unanswerable without this specification. If you are writing an essay on this issue, you have to be sure to add ‘three-dimensional’, which I assume you are asking about.

Even this is difficult to answer. Some thinkers would tell you that there is no difference between them, because this space is what you are perceiving and God only knows if it is real. When you are watching TV, you are not seeing any space at all, but your mind extrapolates from the physical reality of your living space, so that you can understand the events on TV in spatial terms.

The fact that TV images change when you put special goggles on should tell you that ‘space’ is indeed something related to perception.

From this situation you can move easily to the 3D space in which the real events of your life transpire, and then you could say, ‘my mind manufactures an illusion of space around hard objects so that I don’t get hurt by constantly bumping into them.’ If that sounds illogical, consider that your mind does not bother about the air, because usually it will not hurt you. But if you could stick your head out of an aeroplane window at 900 km/h, chances are you won’t get it back.

Take as another example most of the classic Western art that is painted in perspective. What is the meaning of this technique? Essentially that you should look at a picture as if looking through a window. But all those paintings are flat. The spatial illusion is deliberate and exploits the mind’s power to do this.

Philosophically this translates into the problem that the agent — you and I — are in possession of perceptual equipment that has evolved so that we can navigate through the world with reasonable safety. In other words, our understanding of the world as spatial is survival equipment. Accordingly as far as you and I are concerned, space is real. To question its reality is to propose the examination of a world ‘objectively’, i.e. from a non-human standpoint. To do this you would, in practice, need to blindfold yourself, take drugs to desensitise every nerve in your body and immobilise yourself totally. If you wait long enough, the answer will come to you when you are dead.

I am not usually a skeptic. But there are philosophers who pontificate on this issue. Dozens of them have preached the message that ‘all is illusion’. If this were true, then we would be extinct. In any case, it is not genuinely meaningful to carry doubt this far. There are limits to human knowledge, and the difference between real and perceived space brings it well to the fore.

The underlying problem for philosophy is this: that all living creatures have to navigate and negotiate their habitat, and create some form of understanding it. You cannot call this an illusion. In fact, it is the meaning of life. The true illusion is to deny that what we perceive and experience is real. Then we must let robots inherit our world. Although they would also be living in a totally illusory world, they wouldn’t know it and hence such questions would not occur to them. And that’s where the real and only meaningful difference lies.