In this essay, I shall be advancing a couple of arguments ultimately in opposition to the maxim of George Berkeley's subjective idealism that esse est percipi. [1] The bold and simplistic metaphysical nature of Berkeley's philosophical system makes it difficult to attack and refute with any definitive certainty, yet certain arguments provided by him are in my opinion inconclusive and alternatively could be interpreted to support a philosophical system accommodating a corporeal reality. I firstly intend to show that such a system, which I am in favour of and in this essay shall be referred to as corporeal realism, can provide what I believe to be a more adequate explanation of human sensory deprivation. My essay culminates with an attack on Berkeley's subjective idealism from a scientific angle. In an attempt to make some progress on the realism versus idealism debate, I shall be utilising information obtained from research within cognitive psychology on a phenomenon known as 'blindsight', in which patients display the ability to process visual information unaccompanied by any conscious awareness of what they are processing. It may be impossible to "'climb outside' of our senses to disprove what Berkeley says" [2] , but it may be possible to 'climb out' of our conscious sensory perceptions.
According to Berkeley, the being of anything consists in its being perceived, that is, in its being an idea in a mind. "The whole corporeal world, then, can exist only as a set of objects of consciousness, as a system of ideas. [3] " In maintaining the Berkeleyian thesis, however, we need not identify the being of anything with the ideas of only one type of thought, perception, but (broadening his theory) may instead make use of the more general terms "consciousness," "thought," or "experience" [4] For the purposes of my essay, I will be focusing particularly on the relatively modern term "consciousness", broadly equating it with the archaic term 'idea' employed by Berkeley.
The doctrine of idealism is held by some to be vulnerable to Ockham's razor � "to assume that it is indeed the external world that causes our experiences, rather than an exceedingly busy deity, would be a simpler explanation" [5] Yet on the contrary, "not ideas but the notion of a material reality behind ideas was what Berkeley felt to be superfluous" [6] I shall now contrast subjective idealism with corporeal realism in an attempt to show that the rigidly monistic framework of the former can at times detract from its explanatory capacity and clarity relative to the latter.
If reality is immaterial, if it is entirely constituted by ideas, then how I pose are we to interpret the 'mental realm' of a person blind since birth? They are evidently unable to have visual sensations, yet this cannot be due to a lack of vision, as it is physically understood, since there does not exist an external physical world for their malfunctioning visual system to deprive them of; in fact, there exists no physical visual system either. It seems that an idealist would have to state that the 'mental realm' of the blind person differs somehow to that of a normal person and consequently the blind person is unable to have sensations and ideas of a visual nature. What possible reasons could they offer to explain such a deficiency?
To inquire into an idealist's account, consider two people, person A with vision and person B without vision. The idealist can possibly offer that the mind of person B has inadequate faculty to generate or inadequate potentiality to realise perceptions and ideas of a visual nature and therefore unlike person A they are not afforded this portion of the 'idea spectrum'. It is doubtful though whether they would be able to extend upon these vague attributions to provide a more substantial account of these inadequacies and an explanation as to what they signify. If reality for an individual is their partaking and ephemeral 'sharing' in the 'Author of Nature's' constant and omnipresent totality of experiences, then why are a few deprived individuals unfortunately barred from having all possible sensations and ideas? Should we attribute this deprivation to a mentalistic deficiency in the blind person themselves or a selective exclusion from portions of immaterial reality by its author?
Involved it is any idealist's attempt to accommodate within an immaterialist framework the apparent though idealistically 'unreal' physical relation between an embodied percipient and an external physical perceived. For example, when a person voluntarily covers their eyes with their hands and ceases to have visual perceptions, it really does feel as if their material hands are covering their eyes, obstructing interaction between their visual receptors and external electromagnetic radiation. If such an explanation, according to the idealist is only of instrumental significance at best, what alternative explanation could they offer? The occurrence of some inexplicable mentalistic process may very well be an idealist's explanation of such volitional spurious blindness, though it is rather tenuous.
I believe that corporeal realism can provide a more adequate explanation of sensory deprivation as it considers human percipients to be embodied minds interacting with a physical world of which they are a constituent. Put very crudely, human senses, which are a particular and unique composition of physical substance, interact with physical substance of this external world, providing the individual with subjective sensory impressions and ultimately ideas. An uncomplicated account of the absence of vision in a blind person can be provided by simply explaining that the blind person has a malfunctioning visual system, which needs to be functioning properly in order to have visual reception of this external physical reality. This is a very basic outline and of course a more detailed account of vision and lack thereof is the realm of vision science, but it illustrates an important virtue of corporeal realism. By accommodating two distinct entities, an internal percipient and an external perceived, whereby interaction between the two is necessary for sensory impressions within the percipient, an absence of sensory impressions can simply be explained by the identification of some inhibition to this necessary interaction. This inhibition could be a permanent malfunction in a physical sensory system or some temporary physical obstruction.
According to Berkeley, consciousness is the only substantial stage on which the action of the world can take place [7] I propose that if the unconscious sensitivity to and information extraction from an external stimulus as evidenced by blindsight is veracious, then this will have serious implications against idealism.
Blindsight is a form of residual visual ability in which people appear to make certain forms of visual discriminations in the absence of any conscious visual perception. It is found in patients who have suffered damage to the geniculo-striate pathway and is thought to reflect the properties of other visual pathways such as that involving the superior colliculus. Among the visual abilities shown in blindsight are detection of location, movement, stimulus intensity, spatial orientation and shape along with some crude detection of form. While caution must be observed with this phenomenon the evidence points clearly to a form of residual vision that can be detected in the scotoma (regions of total blindness) of patients with cortical blindness [8]
The first clue about residual vision in people with visual cortex damage came from a study [9] of four patients who suffered brain lesions in parts of the striate cortex, resulting in a scotoma. Patients were fixating centrally and asked simply to move their eyes to the position of a brief spot of light shone into their scotoma. The position of the light was varied from trial to trial in a random order. As they could not 'see', the subjects thought the instruction odd, yet all four patients produced patterns of eye movement that accurately reflected the locations of the targets. The effect was not strong but it was statistically reliable. The 'unseen' light was having some control over the subjects' visual responses. [10]
In the example just provided, it is apparent each subject had no conscious visual perception of the spot of light they were presented. They therefore had no idea of the light, which according to a Berkeleyian interpretation implies the light's nonexistence for that individual. Yet in such cases it is extremely plausible that the light did in fact exist. Despite the fact that there was an absence ofconscious visual awareness, it is evident that a degree of residual processing occurred within each subject. Such residual processing I maintain, as corroborated by blindsight researchers, is caused by interaction between the unconscious percipient's subliminal visual sensory system and the objective external spot of light. Hence the findings on blindsight suggest that an absence of phenomenal qualities cannot allow an idealist to dismiss an object's possible existence. If research subjects were staring at a blank board with no spot of light actually being shone on it, then there is no good reason to believe that their eyes should and in fact do move in a determinate manner according to the spatial positioning of the light. It would be an ad hoc and inferior explanation on the idealist's behalf to offer that such unconscious responses are the coincidental result of some parallel and unrelated cognitive functioning.
The findings on blindsight can consequently serve as evidence for an attempt to refute one of Berkeley's arguments against the distinction between primary and secondary qualities. Berkeley's predecessor John Locke granted sensory qualities such as colour, taste, smell, felt warmth or texture and sound, the so-called secondary qualities, were the product of a perceiving mind, though he also held that there exists a corporeal substratum independent from our ideas. Within this substratum inheres the so-called primary qualities, objective qualities essential to anything material such as size, shape, and mobility [11]
Berkeley was one of the first to deny this distinction, a denial he uses for what I consider to be an inconclusive argument against the existence of a corporeal substratum. Consider the visual sensation of a red apple being impressed upon our minds and then the idea of it that is formed. It may well be the case that in our conception of the apple, we are unable to separate its primary round shape from its secondary red colour; every idea of a red apple we form is of something inseparably round and red. From this Berkeley concludes that extension, figure, and motion are only ideas existing in the mind [12] ", for "if it be certain, that those original qualities are inseparably united with the other sensible qualities, and not, even in thought, capable of being abstracted from them, it plainly follows that they exist only in the mind [13]
Such reasoning I believe to be specious. It is the case that when we form an idea of a red apple we depend on the initial visual perception we had of the apple. This visual "apple experience" is a coherent package of shape, size and colour, and we are unable to extract any qualities from this package, e.g. we cannot think of a round apple devoid of colour because every instance in which we have seen an apple, it has had a colour. I propose that this inability to separate an object's primary qualities from its secondary qualities may merely be a limitation of human mental faculties concerned with conscious idea formation, and not an indication of the actual nature of reality. Research conducted on blindsight subjects who have displayed an ability to provide details on one of an external stimulus' primary qualities without any awareness of its secondary qualities strengthens this theory. For example, one blindsight patient was asked to guess whether a stimulus flashed briefly was orientated horizontally or non-horizontally. Unaccompanied by conscious awareness of the stimulus, he was successfully able to perform orientation discrimination on the stimulus. [14] As spatial orientation is a primary quality, such findings I believe suggest that "a physical object is best analysed as a material substratum, in which some sensible qualities inhere". [15]
What possible defence could be sought for subjective idealism in light of the arguments against it just advanced? The blindsight argument I have advanced asserts the independence of reality from percipient finite spirits. One defence may be an appeal to the underlying theological element of Berkeleyian idealism; that the omnipresent perception of God maintains the existence of every portion of reality, irrespective of finite spirit perception. I suppose one could stretch this resort by explaining that blindsight situations are anomalous cases of human perception where for some reason the subject is unable to perceive consciously a portion of reality that they should be able to, a portion that is present nonetheless and is having an effect on them somehow. Such a response raises a few problematic questions though concerning the relation between human perception and God's ideas; indeed it seems that "the position of finite selves in Berkeley's metaphysic is not quite clear". [16]
In Berkeley's idealism, as expounded in the Principles and the Dialogues, finite spirits such as humans have ideas by 'participating' in God's totality of experiences. The case of blindsight though does not exemplify this participation, being rather some sort of implicit semi-participation. Hence, the subjective idealist would have to incorporate some system of gradation for finite spirit participation; a complicating addition I believe would be infirmly grounded. More so, this is assuming that such an inclusion is compatible with Berkeley's idealism.
This essay has proposed and expanded upon several arguments against George Berkeley's idealism. Although Berkeley's idealism provides a seemingly simpler monistic paradigm of reality than corporeal realism, this advantage does not apply to its explanatory capability, which at times can be relatively inadequate compared to corporeal realism, as was illustrated by human blindness. It was subsequently argued that scientific evidence gathered on a psychological phenomenon known as blindsight provides the basis for a tenable alternative argument against idealism. The crux of the argument was, that if according to subjective idealism "external objects are ultimately collections of ideas and sensations [17] then the unconscious reception to an external object evidenced by blindsight patients poses a problem for subjective idealism. The argument primarily established the independence of reality from human percipients and was used to dismiss Berkeley's attack on the distinction between primary and secondary qualities. I did not attempt to disprove the theological guarantee underlying Berkeley's philosophy, though my argument may be utilised as a contribution towards dismissing Berkeley's philosophical system, by eliminating empirical options for the idealist, reducing their argument solely to a speculatively metaphysical one, and generating further problems for them to address. In closing, introspective analysis of our own consciousness does not account for all reality perception and due to its inconsistency, human 'participation' can provide no confirming insight into the nature of an idealistic reality. It may be held by the idealist that human participation is extraneous and that "even if all human minds ceased to be conscious, nature would still exist objectively as the set of God's ideas". [18] This I am unable to disprove, though may I respond to such a comment by offering that perhaps such a position is instrumentally identical to a corporeal substratum framework of reality, the only distinction being one of semantics and ontology, and that the ontology of Berkeley's philosophical system is ultimately no more cogent than that of corporeal realism.
[1] 'To be is to be perceived'.
[2] Bohmer, Otto A, The Philosophy Book, (London: Orion Books, 1999), p. 20.
[3] Audi, Robert, Cambridge Dictionary of Philosophy, (New York: Cambridge University Press, 1995) [Entry on George Berkeley].
[4] Randall, H. J and Buchler Justus, Philosophy: an introduction, (New York: Barnes & Noble, 1970), p.
[5] Robinson, Dave and Judy Groves, Introducing Philosophy, (Sydney, Allen & Unwin, 1999), p. 67.
[6] Randall, H. J and Buchler Justus, Philosophy: an introduction, p. 221.
[7] Robinson, Dave and Judy Groves, Introducing Philosophy, (Sydney, Allen & Unwin, 1999), p. 67.
[8] Parkin, J. Alan, Explorations in Cognitive Psychology, (Oxford: Blackwell Publishers, 1996), p. 37.
[9] Study conducted by Poppel, E., Held, R. and Frost, D. (1973). Research paper "Residual visual function after brain wounds involving the central visual pathways in man. Nature, 243.
[10] Weiskrantz, Lawrence, Consciousness Lost and Found, (New York: Oxford University Press, 1997),
p. 17.
[11] Blackburn, Simon, Oxford Dictionary of Philosophy, (Oxford: Oxford University Press, 1994) [Entry on primary/secondary qualities].
[12] Berkeley, George, Principles of Human Knowledge, (, Penguin Books, 1988 [Originally Published 1710]), p. 56.
[13] Ibid.
[14] Weiskrantz, Lawrence, Consciousness Lost and Found, p. 18.
[15] Audi, Robert, Cambridge Dictionary of Philosophy
[16] Morris C.R., Locke, Berkeley, Hume, ( : Oxford University Press, 1931), p. 98.
[17] Internet Encyclopedia of Philosophy entry on David Hume accessed at http://www.utm.edu/research/iep/b/nerkeley.htm on 16/8/02.
[18] Tipton, I, C, Berkeley, The Philosophy of Immaterialism, (London, Methuen & Co, 1974), p. 93..
[19] Morris C.R., Locke, Berkeley, Hume, ( : Oxford University Press, 1931), p. 98.