In the last section, I came to the result that (1) intentionality is independent of consciousness, and (2) also physical brain structures can have an intentional content. In the present section, I will claim that even physical structures outside the brain can have an intentional content , that is, they are about something or refer to something different from themselves.
Usually, mental states and processes are assumed to be localized in the brain. Many naturalists think that mental states are closely linked or even identical with states of the brain. An exception are functionalists: They hold that the important thing about mental states is not where they are located or what they are made of, but what function they perform. Brentano did certainly not believe that mental, i.e. psychic processes take place outside the head (or the body if we want to include the human heart). But let us see what follows from his definition of the mental as something being intentional:
What about things like Goethe’s poem The Sorcerer’s Apprentice? Undoubtedly, the poem is about something: about a sorcerer’s apprentice and his dramatically failed trial to control the spirits he called in his master’s absence. On the other hand, the poem exists as a physical thing consisting of characters written or printed on paper or, if recited by someone, of sound waves, i.e., of oscillating air molecules. The poem must have any physical, material form to exist, at least outside of one’s brain and mind (its existence in the brain is topic of the next section).
Regarding the poem printed in a book, one may object: it has no intentional content as long as nobody reads and understands it, and when somebody is reading it, the poem’s content arises in his or her mind and becomes mental and intentional by that. And it seems to be true, since neither the meaning of the charcters nor of the words, nor the necessary contextual knowledge is included in the text. All this knowledge must be provided by the reader. Can the text have any semantic content without the reader’s knowledge? Apparently not. Nevertheless, the order of the charcters on the paper was determined by the words and sentences and eventually by the content of the poem, and it is this order which enables the reader to generate the content in his or her own mind. Therefore, the characters on the paper must contain the poem, even if in a peculiar, non-semantic manner.
Let us consider a further example: When I think in words or sentences, my thoughts are about something. When I think the same words or sentences aloud, my speech is about the same content. My speech is a sequence of sound waves, thus someone else can perceive and understand it. It is the sound waves that transfer the content, thus they must contain it anyway in their structure or configuration. However, just as with a written or printed text, the listener needs to understand my language and often needs some contextual knowledge to be able to reconstruct the semantic content of my speech in his or her mind.
One may further object that the content of a thought (or of another mental state) is intrinsic, the content of a sentence spoken or written is not. But is it not rather the thought itself, i.e., thinking as an intentional act which is intrinsic by nature (accessible only for the thinker himself), When I’m thinking, when I’m feeling pain, or when I hear or see or smell something, then all these mental states as such, regardless of their contents, are intrinsic. They are not observable by someone else as long as I do not express them in a physical way in my face, or by gestures, sounds, etc. Therefore, it is not the content itself, which is intrinsic by nature, but the mental state containing it.
A third possible objection may be that the intentional content of language is dependent on the fact that we possess that mind and are conscious beings, thus the intentional features of language are secondary and derived, whereas the intentionality of mental states is primary and original. My answer is: Without having mind and consciousness I could not think these thoughts and not write these sentences, that’s true, But it is not crucial in the context of our investigation. Instead, the fact crucial in our context is that physical structures like sound waves or ink on paper can have an intentional content, and that they resemble thoughts, notions, and other mental states in this regard – even if with the important difference that, in a text or in a speech, the content is present only formally, as a structure or configuration, as the specific arrangement of the pieces of a whole. This specific arrangement keeps and carries the content.
Since they obviously are about something, objects like a poem in a book seem to be both, physical and, in a sense, mental. Karl Popper who also saw this proposed a Three Worlds ontology : In addition to a World 1 of physical objects and a World 2 of mental objects and events in the mind, he postulated a World 3 of objects that are products of the human mind, such as poems, novels, construction plans, scientific theories, myths, symphonies, paintings, sculptures, etc. Regarding their physical existence, these objects are part of World 1, but regarding their intellectual, cultural, or aesthetic contents existing independently of the individual mind they are part of World 3 .
If, however, the content of a construction plan is part of World 3, then the house or the machine built after the plan is, in this sense, part of World 3 as well, because the content of the plan is embodied in them. This is true even for simple everyday products: also the pattern for a dress or the design drawing for a chair are products of the human mind, And eventually, every man-made thing is the embodiment of a purpose and an idea who to materialize it. There is always a plan, even if it is present in the worker’s mind only.
It is not even necessary that an object was shaped by human work: A stick or stone picked up from the ground in order to use it as a tool turns into a thing that answers to a purpose. The stick or stone in the hand is the embodiment of a plan in the mind, and the flower in a girl’s hair is the embodiment her desire to look pretty. In this way, physical things turn to an expression of something mental: of an idea, a target, a desire .
Obviously, there exist a lot of things in our environment which are undoubtedly physical, but exhibit a crucial property of the mental, namely an intentional content: They refer to something which is different from themselves. In a dualist world strictly divided into mind and matter, and also in Popper’s Three Worlds, such objects appear to be somehow Janus-faced, chimeras of matter and mind. In the next chapter, I will propose that not only products of the human mind are of this apparently ‘dual nature’, but all physical objects anyway structured. It’s, so to say, the most natural thing of the world.