Mental states and objects have only mental properties, but only something that is, itself, a mental state or object can have a mental property.
Hence, nothing can resemble—that is, share a property in common with—a mental state or object other than another mental state or object. Berkeley took this point to show that no non-mental cause of an idea could resemble it, whether the relevant idea were an idea of a shape or a color. Berkeley concludes that Locke's distinction between primary and secondary qualities is a grand mistake.
By Merrill Perlman
Reid accepts, for roughly Berkeley's reasons, that sensations cannot possibly resemble their causes—a fact that Reid deploys in his Sensory Deprivation Argument discussed above. Further, he accepts Berkeley's objections to Locke, and takes them to show that no mental events or states, whether sensations or the conceptions of objects that follow them, could possibly resemble any non-mental object. Another reason that Reid cannot draw the distinction between primary and secondary qualities in the way that Locke did is that he denies that conceptions of objects which we have following sensory experiences are to be analyzed as perceptions of ideas.
Instead, these conceptions function to make us aware of qualities in objects that caused the sensations. All of this would make it seem that Reid would simply side with Berkeley and deny that there is any important difference between primary qualities and qualities like colors, sounds, tastes and smells.
Instead, Reid defends the distinction between primary and secondary qualities on grounds quite different from Locke's, grounds that he takes to be immune to Berkeley's criticisms of the distinction. Reid accepts that the qualities which we ordinarily conceive objects to have—whether shapes, sizes and motions, on the one hand, or colors, sounds, tastes and smells, on the other—are genuinely possessed by those objects barring illusions and disorders of various sorts, which are, incidentally, difficult for any direct theory of perception like Reid's to explain.
He thinks that shapes, sizes and motions are intrinsic properties of objects while colors, sounds, tastes and smells are relational properties of objects. But neither secondary nor primary qualities resemble the sensory experiences that they immediately cause in us. Colors, sounds, tastes and smells are powers to produce certain characteristic sensations in us in normal conditions.
Reid, Thomas : Philosophy of Mind | Internet Encyclopedia of Philosophy
To believe that a rose has an agreeable smell or a red color is not to perceive any intrinsic qualities of the object, but is, rather, to perceive that the object bears a certain relation to something else—our minds. Reid writes,. Physical structures of the rose in front of me—the anther in the rose's stamen—produce pollen, which has a certain molecular composition that results in my sensation of its odor.
Other molecules in the petals of the rose reflect light at a certain wavelength which in turn causes in me a certain characteristic visual sensation of red. Ultimately, the rose possesses this relational property because of facts about its molecular structure that account for its producing this odor in a certain way, and facts about me that account for the fact that these pollen molecules enter my nasal cavity, eventually reaching the olfactory bulb, and cause certain sensations in my mind.
But when I am aware of the odor of the rose, I am aware of none of that; I am aware only of the fact that there is something about the rose that makes it cause in me certain sensations in normal conditions. Our conceptions of qualities such as smells and colors are to be contrasted with our conceptions of primary qualities or configurations of primary qualities, such as hardness. Say I'm holding the rose's stem in my hand while I'm looking at it.
I am having two importantly different sensations: a visual sensation of red, and a tactile sensation of hardness. For Reid, neither sensation resembles anything in the object; both give rise to conceptions of the object as possessing certain properties. The visual sensation gives rise to a conception of the object as possessing a particular relational property: its power to produce certain sensations in me in normal conditions. The tactile sensation gives rise to a conception of the rose's stem as possessing a particular intrinsic property: the complex configuration of primary qualities that is hardness.
For both Locke and Reid, we are aware of objects as they are intrinsically only when our awareness is caused by the primary qualities of objects. But for Reid, and not for Locke, we are genuinely aware of objects as they are when our awareness results from the secondary qualities of objects; but we are aware of those objects only as they are relative to us, and not as they are in themselves.
But of the secondary qualities, our senses give us only a relative and obscure notion. They inform us only, that they are qualities that affect us in a certain manner—that is, produce in us a certain sensation; but as to what they are in themselves, our senses leave us in the dark. Secondary and primary qualities are characterized by their relations to the mind perceiving them and to the physical qualities in objects that they signify.
This is not so for secondary qualities. To return to Reid's rose, he writes of the smell of the rose that. One ought not look to Reid's epistemology for a detailed formal apparatus clearly identifying his externalism about justification, for example, even though he can be credited with bringing what we now call externalism about justification into Early Modern philosophy.
We are now in a position to understand the force of Reid's most important response to any argument purporting to show that the external world either might not exist, or might not be anything like the way we take it to be. In one canonical statement of his position, Reid says,. The mistake that the skeptic makes, according to Reid, is to deny the truth of something that is demanded by our constitutions. To perceive an object as possessing a particular property is to have a conception of the object delivered by one's constitution.
What makes us convinced of the accuracy of the conceptions of objects involved in perception is that they arise from our constitutions. But, asks Reid here, why do we find skeptical arguments so compelling? Why would someone sincerely accept the radical skeptical conclusions following from Descartes's hypothesis of the evil demon? Ultimately, we think that such arguments lead to their conclusions because we accept certain logical principles—such as the law of non-contradiction, or modus ponens—which appear to us to be self-evident.
But to say that such principles are self-evident is just to say that we cannot help but accept them. It is not to offer any non-circular justification of those principles. But the irresistibility of a belief is a very good indicator, Reid thinks, that we hold that belief merely because of the way we are built, merely because of our constitution. But then the skeptic has merely placed the skeptical conclusion on the same footing as the common sense belief about the external world: both rest on something that we are compelled to believe by our constitutions.
However, in order to overthrow common sense, the skeptic must place the skeptical conclusion, rather, on a firmer footing than the common sense conclusion. Thus, the skeptic gives us no reason to reject common sense beliefs about the external world. Reid has defended common sense through construction of a direct theory of perception that avoids the pitfalls of the Way of Ideas' representational theory. Reid develops his account of causation in light of Hume's account.
As Reid sees it, Hume starts with the assumption that if we are to learn what causation is, we must first determine from what aspect of our sensory experience the concept of causation is derived. Hume would put the point in terms of the Way of Ideas as follows: we must determine from what impression our idea of causation is copied. However, Hume believed he had discovered that there is nothing in our sensory experience corresponding to our ordinary notion of the causal relation.
In an inversion of the empiricist method attributed to Reid above, Hume believed that causes necessitate their effects, then he followed this commitment by arguing that we lack sensory awareness of this necessitation. We see the first billiard ball hit the second. We see the second move. We do not see the movement of the first assure , or necessitate, the movement of the second. So Hume concludes that causation must be something different from what we take it to be ordinarily. But what is it?
To answer this question, we must determine from what sensory experiences we derive the idea of causation. It turns out, as Reid reads Hume, that the sensory experiences that give rise to our idea of causation are sensory experiences of what Hume calls constant conjunction. The heating of the water is regularly followed by the water's boiling. To say that the one event causes the other is just to say that the two events always co-occur, or that there is a brute law linking them. This is not to say that the first event necessitates the second.
The necessitation that we ordinarily take to be involved in causation is not in the world; it is in our heads as an expectation arising due to previous experience. Reid accepts much of the negative side of Hume's view of causation while rejecting Hume's assertions of the import of those negative discoveries. Reid agrees, that is, that we have no sensory experience of the necessitation of an effect by its cause.
But this does not imply our ordinary concept of causation is mistaken. Instead, Reid thinks, the concept of causation is not an idea copied from a sensory impression in the first place. Reid's complex thoughts here are tied to perception and the role of sensations in perception.
McConnell follows in Reid’s footsteps
See 3. For him, sensations never bear resemblance to the qualities they help us to perceive.
It is hardly a surprise, then, that the sensory experiences from which our thoughts about causation spring bear no resemblance to the causal relation. But this fact no more undermines our concept of causation than the lack of resemblance between our sensory experiences of ordinary physical objects and those objects themselves undermines our thoughts about such objects. Like our thoughts about objects, our thoughts about the causal relation are genuinely about the causal relation, despite the fact that the sensations from which those thoughts spring, i.
We have no sensations resembling necessitation, and, yet, causes necessitate their effects.
However, Reid also offers criticisms of Hume's view of causation that can be accepted independently of the Reidian view of perception and sensation. Two of his most influential criticisms are of Hume's view that our ordinary concept of causation is reducible to the relation of constant conjunction. Reid's point is that if the relation of causation is really that of constant conjunction, then the first time that two types of event are conjoined, the first cannot be the cause of the second.
If there is no history of conjunction, there is no causation. It would seem to follow from Hume's definition, for instance, that if an earthquake razes Mexico City, and no earthquake has ever done so before, then the earthquake is not, in fact, the cause of the city's fall, an absurd implication. This objection might not show Hume's theory is mistaken—we omit consideration of it further here—but it does pose a question with which any Humean must wrestle: Which constant conjunctions are the genuine ones on the basis of which the causal relation can be said to hold, and which are not?
The more specifically any two events are described, the more likely that there will be no history of conjunction of the relevant sorts of events. But what degree of specificity or generality in description is the right degree? The problem is made clearer by Reid's second objection to Hume's analysis of causation and constant conjunction. Since we don't ordinarily think that day is the cause of night, or vice versa, Hume must deny that the two are actually constantly conjoined, or, rather, he must insist that the constant conjunction between the two of them is not of the right sort for the relation between them to be one of causation.
Hume thinks that there is causation between two events just in case there is a law linking them and also thinks that there is a law linking two events just in case they are constantly conjoined.
Reid's first objection shows that it is not the case that wherever there is no constant conjunction there is no law. His second objection shows that it is not the case that wherever there is constant conjunction there is a law.