Visualization of Unprecedented Object as the Main Issue in Berkeley's Book "The Principles of Human Knowledge"

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The issue of whether or not one can visualise an unperceived object is one raised by Berkeley in ‘The Principles of Human Knowledge’. In his famous ‘tree’ example, he claims that to visualise ‘a tree as existing unperceived’ is a contradiction, because the very act of visualising it entails that it is perceived, and so one is no longer visualising an unperceived tree.

The issue here is what it means to visualise something, and whether that can be said to involved perceiving it.

If so then it is an impossible task, but if visualising is distinctly different to the act of perceiving, then it is plausible that one might visualise an unperceived object.

Let us first examine what it might mean to visualise an unperceived object. Williams discusses the idea of someone in the 19th Century visualising the South Pole. At that time, the South Pole was an unperceived object in the extensional sense, as no one had ever led an expedition there, so it had never been perceived by humans.

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Hence for a person in this era to visualise the South Pole would have meant that they were visualising an object that was unperceived. Therefore it is possible.
However, there is a sense in which visualising an object which is unperceived is different to visualising an unperceived object, and it is in this distinction that the difficulty lies.

Williams’ example is taken in the extensional sense, whereby being unperceived is a property that the object of one’s visualisation happens to have.

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Instead what it seems Berkeley intended is that the visualisation strictly involves an unperceived object in the intensional sense, whereby being unperceived cannot be separated from the project of visualising the object.

For example the intensional sense would involve visualising Oscar as my boyfriend, rather than visualising Oscar, and Oscar happens to be my boyfriend. Therefore this example fails to demonstrate visualising an unperceived object in the correct sense.

As an example of visualising an unperceived object seemingly cannot be found, it must be explained why in fact we cannot achieve such a feat. In order to do so, a definition of ‘visualise’ must be proposed, and one such definition mentioned by Williams (although later to be rejected), that seems also in accordance with the views of Peacocke is that visualising is “thinking of one’s self seeing’, where thinking of’ seems to be used interchangeably with ‘imagining’.

From this definition one cannot visualise an unperceived object, because it is incoherent to talk of one imagining himself seeing what is unseen. As imagining seeing is the same as visualising, and being unseen is the same as being unperceived, it can be seen as logically contradictory to talk of visualising an unperceived object.

However, this argument does seem to rely upon the definition of visualising as ‘imagining one’s self seeing’, which is something that Williams comes to reject. He argues that it need not involve imagining one’s self seeing, but could be from any perspective, as it does not necessarily involve one’s own self, ‘except as the person who…does the visualising’.

For instance it would be perfectly acceptable to visualise a tree without being yourself involved in this visualisation, as you as the individual who is visualising does not need to play a role in the world of your visualisation. Therefore this definition is not an acceptable one for a visualisation, so cannot be used to argue that one cannot visualise an unperceived object.

Yet Williams is perhaps unjustified in his argument. This is because there is a very definite sense in which one’s own visualisation cannot exclude one’s self. As Peacocke says, imagining always involves imagining from the inside a certain (type of) viewpoint’ such that the person with that viewpoint could give details from that viewpoint and declare themselves to be in that certain location within the visualisation.

It is not possible for a person who is visualising to say that they are not in the ‘conscious state of visualising an object becaus say that involves thinking in a way ‘made available to the thinker by his actually being in those states’.

It is impossible to visualise a tree, realise one is visualising a tree, yet deny that one is involved in the visualisation of that tree as a fact of human psychology. Therefore it still holds that one cannot visualise an unperceived object as one is essentially involved in the visualising in a way that means they perceive the object that is to be unperceived.

There is a further reason to argue that one cannot visualise an unperceived object that can be found in Williams’ paper, and this is achieved by exploring the difference between visualising and imagining. He gives the example of a man who has recently been to a Bonnard expedition where he observed baths with women in, and so having this on his mind is unable to visualise a bath devoid of a woman.

Yet surely we can say he is able to imagine a bath without a woman in – the faculty of imagination has not been impaired by his day at the exhibition, yet he cannot create an image in his head of a bath without also visualising a woman in it. Therefore if one can imagine something but not visualise it, the two must be different faculties of the mind.

Hence when we are inclined to argue that one can visualise an unperceived object, what we are really recognising is that one can imagine an unperceived object. ‘When we imagine by way of visualising, we can properly be said to imagine something lacking an element which is present in what we visualise’ due to the difference between the two phenomena, and therefore while we can imagine an unperceived object we cannot visualise one.

However, Williams argues for the conflicting view by later exemplifying a way in which one can visualise an unperceived object. He makes a comparison between visualising and watching a theatre production. For instance when watching Othello, ‘we … see what is happening in that world, but not in the same sense as that in which we see the actors’, just as when visualising we can be said to imagine a different world.

So as with watching a play, we can see what is happening in the other world’, yet do not have a viewpoint from within it. When I watch Othello strangle Desdemona, we would agree that I have seen someone strangled in that world yet I have still never actually seen anyone be strangled, and the actor playing Othello has certainly not just strangled someone.

Therefore there can be no reason at all for insisting that the point of view is one within the world of what is visualised’ just as one’s point of view is not one from within the play. Therefore to visualise an object is not to perceive it in any way, as it does not involve a viewpoint in the same ‘world’ as that which is being visualised. Therefore in this way one can visualise an unperceived object.

Yet Peacocke refutes this by criticising Williams’ example. He argues that the example of a play is not fitting, because visualisation is something that occurs within an individual, whereas there is no such possibility for this with a theatre production, and indeed due to the nature of theatre, the director has the freedom to portray the ‘world’ from whatever point of view he wishes.

He even has the power to portray it as someone else’s visualisation. Therefore it is not an appropriate example, as ‘it is in the nature of the sensory imaginings with which we are concerned that to imaging something is, in part, to imagine an experience from the inside’, which cannot be compared to the ‘world’ created by theatre.

Contrary to Williams’ claim, there is a reason ‘for insisting that the point of view is one within the world of what is visualised’, because one is only capable of creating any mental image of something which includes their point of view. It is beyond the capabilities of the human mind to detach itself from any ‘world’ created by our mind; ‘no matter where you go or what you do, you live your entire life within the confines of your head’l. Therefore it is just a fact of human psychology that one cannot visualise an unperceived object.

In conclusion, essentially one cannot visualise an unperceived object. Along with the reasons discussed, the issue centres around what is necessary to a visualisation, and clearly one necessary aspect is the visual – that the thing being visualised is seen. As such it is impossible to visualise an object that is unseen, or unperceived, because this would cease to be called visualising. Therefore it can be seen that it would be a logical impossibility, as visualising is a form of perceiving, and so one would be required to perceive the unperceived, which is incoherent.


  1. Josephson, Terry., Xplore Inc, 2012., accessed March 14, 2012.
  2. Peacocke, Christopher. “Imagination, Experience, and Possibility: A Berkeleian View Defended.” Essays on Berkeley; J. Fosh and H. Robinson (editors) Oxford Clarendon Press. 1985. 19-35. Print.
  3. Williams, Bernard Arthur Owen. “Imagination and the Self.” Problems of the Self; Philosophical Papers 1956-1972. Cambridge [Eng.: Cambridge UP, 1973. 26-45. Print.

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Visualization of Unprecedented Object as the Main Issue in Berkeley's Book "The Principles of Human Knowledge". (2021, Oct 05). Retrieved from

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