What Are Objects Doing When We Are Not Looking?

Like every child who watched Toy Story as a child, that question came to my mind: What do these toys do when we are not looking at them? Or to expand it further: What are these objects doing when we’re not looking?

This series, which will consist of two parts, will include the first step in understanding the quantum universe, which is actually a vast world. In the first part, we will interpret the philosopher Berkeley’s somewhat disturbing thought experiment and its philosophical point of view. In the second part, we will examine the particles that behave completely differently when we look, by talking about the “Double Slit Experiment”, which Richard Feynman calledthe essence of quantum mechanics“, the mystery of which we still cannot fully solve even today. Let’s start the first part if you have your tea or coffee!

Would it make a sound if a tree fell in the forest while no one was watching it?

Okay, I know it doesn’t seem logical at first. Of course, objects continue to move or stay where they are, even if we are not looking. Even if we are not around, if a tree falls in the forest, it will make a sound. After all, the world doesn’t revolve around us. Or is it actually? Could the world be just us?

This thought experiment was introduced in 1734 by the philosopher George Berkeley. Berkeley’s famous saying is: Esse est percipi. That is, to be is to be perceived. If something cannot be perceived, it actually does not exist. To get to the root of this question, let’s rewind history a bit and move on to another philosopher: John Locke.


John Locke proposed that objects have primary and secondary qualities to indicate how accurate our perceptions are. Primary qualities were qualities possessed by physical objects. These were completely objective and did not change according to our perceptions. For example, let’s consider an apple. Qualities such as hardness, density, weight, length, and height of the apple are the primary characteristics. These are real features. Secondary qualities, on the other hand, were not real, and they were features that changed completely according to our perceptions and lived in our minds. Just like viruses that become alive in the human body but die if they can’t find a place to stay. They were actually dead traits if they weren’t built into a mind. So it would differ from person to person. Qualities such as color, taste, and smell are secondary. That is, one person might say the color of an apple is red, while another might describe it in dozens of different ways, such as deep pink or burgundy. Because of this difference in perception, John Locke actually claimed that the secondary qualities of the apple were entirely in our minds and said that it was not real.


If different people measured the mass of the same apple, they would find the same exact result. This was the primary attribute and was entirely related to the object itself. But it was very likely that it would spark hours of discussion about color. So this was the secondary quality that lives only in our minds and consists of our perceptions.

Even More: Actually Nothing Is Real!

George Berkeley was impressed by this idea of ​​John Locke. After much reflection, he came to the conclusion that Locke’s concepts of primary and secondary qualities were in fact inseparable. Let’s think about the apple again. According to Locke, the shape of the apple was a primary feature and was unchangeable. In this way, it could be perceived directly. Berkeley, on the other hand, argued that some qualities cannot be perceived by completely ignoring others. It was not possible to perceive the shape of an apple without considering its color. More generally, he stated that in order to perceive the primary qualities of an object, we also need secondary qualities. If we ignore secondary traits, we won’t be left with an apple. Let’s do a test. Close your eyes and imagine an apple with only primary characteristics such as length, weight, mass, and shape. It should not have secondary features such as color, smell, or texture. Chances are, you actually visualized something black or white while trying not to imagine the color of this apple. In doing so, however, you have only changed the color of the apple that lives in your mind. You couldn’t remove the color feature. So in fact it is impossible to imagine that something is colorless or non-textured.


Based on this inference, Berkeley arrives at the following conclusion. Locke is right. Indeed, secondary qualities such as color and smell live only in our minds and are only perceptions. However, primary characteristics such as shape and length cannot be considered independently of secondary ones. Therefore, both primary and secondary qualities are only our perceptions. As a result, nothing that actually happens around us is real and there is no such thing as matter. There are only perceptions!

Berkeley explains this situation in one sentence: To be is to be perceived!

Something can exist as long as it is perceived. This thought is extremely frightening. This also means that unless someone perceives you, you don’t actually exist. Let’s exaggerate a little more and think about the time we slept. The thought that will make you lose your sleep is exactly this: you cannot perceive yourself while you are sleeping. So, if you don’t have anyone around you who watches and never blinks, you cease to exist for a while. The thing is, you disappear while you sleep!

You may have this question in mind. In Berkeley’s chilling idea, nothing was supposed to ever exist. How then can we exist?


Something was there because someone was always perceiving us. Berkeley thought it was God who was watching us all the time and keeping us from disappearing. According to Berkeley, we could all exist because God watched us without blinking.

Now, back to our initial question. Would anyone hear if a tree fell in the forest when no one was there? Berkeley’s answer would be “no”. An object exists as long as we perceive it. Therefore, not only a fallen tree in the silent forest but also all the objects that we do not look at will disappear until we look.

If I am not there, it does not exist either!

Understanding that everything in the universe consists of our perception gives one interesting self-confidence.

The Persian poet Omar Khayyam had pointed out that contrast nine hundred years ago:

Without me, there are no roses,
without me, there are no cypress,
no red lips, no fragrant wines…
No mornings, no evenings, joys,
There are no worries, the world exists as I think;
if I am not there, it does not exist either!

If you wish, you can listen to these lines accompanied by Serenad Bağcan‘s voice and Fazıl Say‘s piano!

Another sad but true saying on this subject is as follows: When the last person who remembers you dies, you will never actually exist!

In order to continue to exist, we wish to leave useful and permanent works to the next generations 🙂

References and Further Readings

Berkeley, G., & Dancy, J. (1998). A treatise concerning the principles of human knowledge. Oxford University Press.

crashcourse. (2016, March 15). Locke, Berkeley, & Empiricism: Crash course Philosophy #6. YouTube.

Erdonmez, C. (1970, January 1). If a tree falls in the forest, will anyone hear? If a tree falls in the forest, will anyone hear?

Images not cited are used through Canva Pro with a royalty payment.

The proofreading has been done by Asu Pelin Akköse and Mete Esencan.

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Mete Esencan

Hello everyone! I'm Mete Esencan. I am a graduate student in the Department of Chemistry at METU. I was planning to establish a platform by combining the research knowledge I gained during my basic science education and the management experience I gained in the METU Chemistry Society, which I was in charge of for three years. For this purpose, in February of 2021, I took the first step and established the OkButWhy, a platform where we can write articles as if to chat about science, art and philosophy. I wish everyone a pleasant reading!

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