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Higher-Order Thought and Higher-Order Perception Theories of Consciousness

This article was submitted as the Final Paper of the course ''PHIL 417: Philosophy of Mind/Nature of Consciousness''.

Abstract The term higher-order refers to a mental state that is directed to another mental state. Whether the higher-order process is a perceptual or a thought-related (verbal) one have been a topic of debate. In this paper, two of higher- order theories, those of William Lycan’s higher-order perception (HOP) theory of consciousness and David Rosenthal’s higher-order thought (HOT) theory of consciousness will be compared; the differences, similarities, strengths and weaknesses, as well as comments and objections of other respected philosophers will be presented.

Keywords: higher-order perception, William Lycan, higher- order thought, David Rosenthal, consciousness Introduction

Among the major ongoing disputes in the field of philosophy of mind is concerned with the nature of conscious mental states. A mental state is defined as a state that corresponds to beliefs and desires, knowledge and thoughts, mental images, emotions and moods, and perceptions and sensations. Philosophers argue that these states are not usually conscious themselves. They become conscious when another mental state is directed at them. Higher-order theories explain how mental states become conscious. When a mental state is conscious, because another state is consciously –not to be confused with intentionally- directed at it, it is called to be higher-order. Despite the fact that many of these mental states are conscious, we also experience nonconscious mental states. Some may argue that a mental state is already a conscious one, or that a mental state requires a conscious agent. However, there are times, for instance, when we are not aware of our feelings, thoughts, or desires. Sometimes, someone asks about them and we suddenly notice we are sad about something or notice a sensational stimulus that we were not aware of.

Despite the fact that it seems obvious that all mental are conscious, our mentality does allow room for nonconsious states. One may not be consciously aware of his desire to become a very successful pilot; he would just be experiencing it. Of course desiring is a propositional attitude. A propositional attitude is a diverse class of mental states that involve relations to thoughts. Propositional attitudes are typically described by verbs like believe, hope, expect, desire, want, and such. To give a perceptual example, one may not notice his spouse’s new haircut until she asks about it. He then becomes aware of it. These kinds of instances reflect as to how one may have mental states that are not conscious.

Higher-order theories propose different approaches as to how mental states become conscious. There is an extensive literature concerned with the topic. Two of these theories are David Rosenthal’s higher-order thought (HOT) theory and William Lycan’s higher-order perception (HOP) theory. The HOT theory argues that a mental state becomes conscious when the person has thoughts about it. The HOP theory attests that other than the sensory organs, humans have internal senses that scan their perceptual outputs — the first-order perceptions and that for one to be conscious of something, one ought to see, hear, or perceive it in some way.

This paper intends to discuss the two theories of consciousness mentioned above. Higher-order thought (HOT) theory by Rosenthal and higher-order perception (HOP) theory by Lycan will be the main focus of discussion. Following the introduction, I will first delve into the HOT theory, then to the HOP theory. The discussion part will highlight their differences, strengths and weaknesses, and will give place to objections from other philosophers. Some philosophers reject the higher-order theories altogether. Their objections will be shortly mentioned, yet, will not be the focus of this section. Furthermore, this part will examine the relationship between intentionality and consciousness and will claim that because intentionality is an important component of conscious action, the HOT theory seems to stand better than the HOP theory.

Rosenthal’s Higher-Order Thought (HOT) Theory of Consciousness 

Rosenthal (1997) highlights the fact that some mental states’ relation with their consciousness is stronger than some others’ (p. 732). This makes sense, considering we have different kinds of mental states. Some require more cognitive attention, and some not. In his article where he draws the distinctions between creature, state, and transitive consciousness, Rosenthal also mentions his higher-order thought (HOT) theory of consciousness (1993). He defines the term transitive consciousness:

“When a creature senses something or thinks about some object, we say that the creature is conscious of that thing. A full description of a creature’s being conscious of something always involves mentioning the thing the creature is conscious of. (…) we may call this property transitive consciousness” (p. 355).

He argues that a conscious mental state is a state one is transitively conscious of. He points that for these states themselves to become conscious, one ought to have third-order thoughts about them. Besides, when one’s mental states are conscious, but not in an introspective way, one is not aware of his HOTs. In times when we are aware of our conscious mental states, these are introspective conscious states (1993, p. 362). “HOTs are treated as cognitive states involving some kind of conceptual component’’ (Gennaro, 2004, p. 3).

A mental state that is not a conscious one is one that we are not aware of. One may, for instance, desire something, but not be aware of it. Sometimes we recognize that we are feeling anxious when someone points it out to us.

What Rosenthal proposes, higher-order thoughts, require verbal ability. In addition, thinking is a cognitive process, which one is more attended in (than one is in perceiving). The person is more involved, and intentionally. A mental state is an intentional mental state when it is about, or directed at some object. I believe, for this reason, HOT intuitively makes more sense. 

Lycan’s Higher-Order Perception (HOP) Theory of Consciousness 

The higher-order perception theory is one of the higher-order representation (HOR) theories of consciousness. HOR theories mainly argue that “the idea that what makes a mental state conscious is that it is the object of some kind of higher-order representation. A HOR is a meta-psychological state” (Gennaro, 2004, p. 1). The roots of higher-order perception theory can be traced back to John Locke. The view is mostly now being followed and defended by David Armstrong and William Lycan. John Locke claimed “consciousness is the perception of what passes in a man’s own mind” (1689/1975). This view paved the way to the inner-sense theory, a version of the higher-order perception (HOP) theories. And as Armstrong puts it “introspective consciousness…is a perception-like awareness of current states and activites in our own mind. The current activities will include sense-perception: which latter is the awareness of current states and activities of our environment and our body” (what is consciousness, p. 61). “According to the higher-order representation theories of consciousness as a mental state or event is a conscious state or event just in case it (itself) is the intentional object of one of the subject’s mental representations” (Lycan, 2004, p. 93). Lycan expands his explanation and adds that the attention mechanisms are devices that function to coordinate information about ongoing psychological events and processes (1995, p. 755).

HOP theory argues that people have “second-order non-conceptual and/or analog perceptions of their first-order states of perception” (Carruthers). What is meant by perception is the “consciousness of what is going on in one’s environment and one’s body” (Armstrong, p. 723). Armstrong addresses the term perceptual consciousness. He refers to the “special link between consciousness and perception” (p. 723).

The theory argues that having sensations require there is something like to be in that state. We are involved in, for instance, seeing the color blue, or hearing the violin, or sensing the itch. It must mean that the mere existence of these states require consciousness. There is no such thing as what it is like to have these sensations unless the sensation is conscious (Rosenthal, 1997, p. 733). The difference here would be what Rosenthal calls the introspective consciousness. What he means by introspective consciousness is a mental state which we are conscious of in an attentive and deliberate way (1993, p. 356).

It is a sensory process and is immediate. HOP theory supposes that one is conscious of things when one sees, or hears them, or perceives in some way, whereas, Rosenthal emphasizes thoughts. An itch, pain, or tickle are all perceptual and, according to HOP theory, feeling the itch, the pain, or the tickle imply consciousness.


The main difference between the two is the former focuses on the necessity of a verbal process –thoughts-, and latter perceptual sensations. To dig this deeper, here, I will mention the relationship between consciousness and intentionality. Robert Lurz is one of the philosophers who reject both of the theories and proposes another theory called same-order representationalism (SOR) that emphasizes the intentionality, and argues what makes a mental state conscious is one’s awareness of its intentional content (Lurz, 2004).

“Mental states exhibit intentional or sensory character” (Rosenthal, 1997, p. 740). As to my understanding, for a person’s –or a creature’s- states to be conscious it ought to be intentionally and actively involved. Simply perceiving does not seem adequate for a state to be conscious. Considering this point, the HOT theory seems to be more plausible. Thinking implies intentionality, whereas, perception implies immediacy and is an automatic system.

Likewise, Rosenthal (1997) opposes to the HOP by stating that “perceptual sensations can occur without our being aware of them. Even pain can go wholly unnoticed, and so can exist without being conscious.” (p. 731). Although, pain is not always considered to be a mental state. Besides, Rosenthal’s criticism may apply to thoughts as well. There can and have been times when thoughts just pass our mind, even if they are about another mental state, and that it is not that they simply pass and go; rather, we may not be paying (conscious) attention to them.

For HOTs to exist, language ability would be necessary. For a creature to be able to have thoughts about its mental states, it has to have linguistic abilities. Thinking requires verbal faculty. Unless a nonlinguistic creature somehow evolves, at least to be able form words, it cannot think, cannot have HOTs, and therefore, cannot have conscious mental states. Even though some doubt the necessity of language for thought formation –agreeing upon the necessity of thought for language-, some philosophers, think that the involvement of language in thinking is restricted to specific kinds of thought, to conscious propositional thoughts (Carruthers, 2005). A plant, perhaps, does not consume cognitive effort to think about its need/desire for water. It automatically drains it from the earth. This is not to claim that plants –or animals or infants- do not have consciousness. My point is rather their cognitive capabilities, nervous systems are not sophisticated enough to let them have higher-order thoughts. Another distinction to point out is the possibility or occurrence of visual or imaged thinking. Sometimes we do not think in a verbal way. Thinking that “the crowd in the airport will probably make you late and therefore, you have to act quicker” is a different kind of thinking than seeing the vision or picture of yourself in a red room. Would this be a question of the HOP theory because it involves image perceiving or question of the HOT theory because it essentially is thinking? I am not sure. The HOP theory seems to leave many questions unanswered.

Additionally, if the HOP theory is true, a person who is incapable of seeing, hearing, touching or feeling, tasting, smelling, or who lacks all of its perceptual abilities, cannot have conscious mental states. This would make one think that the theory essentially links consciousness to perceptivity only. And this seems to be problematic because does the person who has no perceptual no ability conscious mental states? Can this person not have thoughts, beliefs, desires, hopes, and hence have higher-order thoughts of these attitudes?


It is hard to say which theory is superior to the other. Some philosophers argue that the HOP theory ultimately reduces to the HOT theory (Güzeldere, 1995). And some philosophers are in favor of the first-order theory of consciousness.

Among the common objections to the higher-order representation theories –and higher-order thought- theories of consciousness is that they are circular and result in infinite regress since consciousness is defined in terms of HOTs. Besides, since, according to the HOT theory, a conscious mental state must be accompanied by a HOT, that too, in turn, must be accompanied by another HOT, and so on (Gennaro, p. 5).

A second common objection regarding the HOT theory is, as also discussed above, is concerned with animal and infant consciousness. It argues that animals and infants do not contain the conceptual sophistication that is necessary for HOTs. Cats cannot have thoughts, especially higher-order thoughts, which would allow them to contemplate further on their current mental states. In response to this, Carruthers argues that animals and infants do not have phenomenal consciousness (1989). Whereas, Gennaro states that most higher-order theorists do not want to accept that animals and infants lack consciousness as a consequence of defending the theory and he adds saying that this fact cause some to shy away from forms of higher-order theories (2004).

Another criticism against the theories is the “problem of the rock”. Proposed by Alvin Goldman (1993), the argument argues that when one has a thought about a rock, the rock certainly does not become conscious. However, this objection does not quite apply to HO theories. As Rosenthal, Lycan, and Gennaro responds in various sources, there is fundamental difference between a rock and a mental state. Moreover, HO theorists, try to explain how mental states become conscious states.

Even though it may not be right nor possible to claim one theory is true and the other is not, the higher-order thought theory seems to be more successful in explaining how mental states become conscious. It at least rises less question marks and is built on a more solid base, considering the weaknesses mentioned regarding the higher-order perception theory.


The fundamental difference between the two higher-order theories is that the HOT theory mainly explains conscious mental states by thoughts, and the HOP theory as by having perceptual inputs. I believe the HOT theory proposes a more complex and consistent explanation as to how conscious mental states occur.

Noticing the noise from the construction site hours later, and having a thought about this experience of hearing, having a higher-order thought, would make the sensation conscious, according to the HOT theory. HOP theory would suggest that merely hearing the voices mean that one’s state is conscious. It is not, in my opinion, neither possible nor right to assert that one of the two is true and the other is false. Nevertheless, higher-order thought theory does seem to be more plausible. It sets limitations about the consciousness of animals and infants. One can conclude that these cannot have HOTs and cannot have conscious mental states, which intuitively sounds reasonable. The HOP theory, on the other hand, in case would argue that nonlinguistic creatures, if they are able to have perceptions, can have conscious mental states. This needs to be further explained so that our questions do not remain unanswered.


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Carruthers, P. (2005). ‘Conscious thinking: language or elimination?’. Consciousness: Essays from a Higher-Order Perspective, pp. 115-133. New York: Oxford University Press.

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Lycan, W. G. (). ‘Consciousness as internal monitoring’. In Rocco J. Gennaro (ed.), Higher-Order Theories of Consciousness: An Anthology, pp. 755-

Locke, J. (1689/1975). An essay concerning human understanding. P. Nidditch (ed.). Oxford: Clarendon.

Lurz, R. W. (2004). ‘Either FOR or HOR: a false dichotomy’. In Rocco Gennaro (ed.), Higher-Order Theories of Consciousness: An Anthology, pp. 227-254.

Rosenthal, D. M. (1993). ‘State and transitive consciousness’. Consciousness and Cognition, 2(4), pp. 355-363. doi: 10.1006/ccog.1993.1029.

Rosenthal, D. M. (1997). ‘A theory of consciousness’. In Block, Flanagan, & Guzeldere (Ed.), The Nature of Consciousness, pp. 729-753.

Rosenthal, D. M. (2002). ‘Consciousness and Higher-Order Thought’. In L. Nagel (ed.), Encyclopedia of Cognitive Science, pp. 1-10. London, UK: Macmillan Publishing.



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