This series begins with The Machine in the Ghost

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The previous few parts of this series focused on the sensory wall that separates reality from the knowing brain and on the reality that lies on the other side of that wall. On the brain side, we have only taken a small step away from the raw input from the sensors of our various sensory modes, but we have already defined a process that results in representation. There seems to be some large steps between a representation and its meaning, however. Here, we will fit meaning into our emerging theory of brain.

There is an entire philosophy dedicated to what meaning means. Meaning is a major theoretical concern of linguists and, more recently, a very important practical concern of the purveyors and users of the unbelievable heaps of information that the world is churning out. We have the Semantic Web, and knowledge engineering, and data management systems. An entire industry of companies that offer to help large corporations deal with internal and external information is growing, and the biggest companies on the Internet are based on sophisticated search functions. All of it rides on the giant little question of what something means. In ordinary talk, we are comfortable with what the dictionaries tell us: meaning means "intention" or a purposeful result, "importance (to someone, usually emotional or beneficial)", and "necessary consequence or result". The sense of `meaning' that we are most interested for now is "of import (to someone)". We will view meaning as inherently subjective and go from there.

The brain models the structure of reality by recognizing patterns in large sets of very local sensory signals through a simple process of association, something networks of neurons are very good at. From our definition of reality in Reality, Dimensions and Ontology, we understand that the complexity of reality is potentially unfathomable; there is far more possible information than can be directly sensed or inferred by brain-like processors from even very large sensory samples. From our model of sensing and the processing of sensory input, we can infer that only some part of reality, possibly some quite tiny part, is modeled by the brain. What the brain can model depends on what dimensions its senses can measure and what derivative dimensions it can produce through association. This raises an interesting question. How does an organism come to be able to detect the particular aspects of reality that it does rather than others? The answer to that question is also the answer to the question of the meaning of meaning.

We've asserted that meaning is transitive; there must be a thing to which an event or state has meaning. It makes no sense to speak of an event as having an absolute meaning that is entire to itself. What does it mean when a photon excites a certain molecule in the rod cell in an eye, for example? Well, we can speak of meaning here only in the limited sense of consequence, or a causal event chain. The photon causes the molecule to change the electrical potential of the rod cell, which causes the cell to fire off a signal that represents the photon-molecule event. What does that signal mean? The firing is a representation of the photon event, so we can say that it `means' (represents) that a photon has hit the cell. But to what thing is this representation significant? If the process ended with the firing of the rod cell, it would have no more import than any other of the uncountable events and chains of events that make up the dynamic universe of reality. A representation only has meaning when it is relevant to a goal of an organism.

Definition: A meaning is the effect of a representation of reality on the goals of an organism.

Definition: A subject is an organism whose goal-oriented behavior can be altered by representations.

Definition: A goal is a state to which an organism tends by nature of its organization.

Tying meaning to the success of an organism by way of effect on goals gives us a basis for understanding how organisms come to have the senses that they have. That basis is ordinary evolutionary genetics. The processes of evolution and adaptation result in organisms that have the particular senses that provide information that is most meaningful to them. Meaning is the criteria a subject uses for sorting, relating and attending to the sensed structures in reality that are the most important to it in terms of its goals.

If we accept this definition, then we are urged to accept that meaning divides basically into benefit and harm, where beneficial is something that helps achieve the organism's goals and harmful is something that deters those goals. For example, some mobile protozoa can sense light and move toward it because it benefits them; others may do the opposite because light harms them.

Clearly, meaning is going to get a lot more complicated than the binary choice between benefit and harm as the ability to integrate and associate sensory input into complex inferred structures in time and space increases. The human brain creates an amazingly detailed model of reality. The size of that model implies that much of it consists of very complex representations that have been built up by many levels of association. The more complex and overlapping these representations, the more shades of gray appear between the black and white of harm and benefit. Our facilities for memory and imagination greatly expand our ability to defer relevance and postpone assignment of meaning to events and their representations with respect to the present and future, and even the past. Meaning may take on further aspects when we get to consciousness, symbols and language. Nevertheless, all that complexity and gradation must grow upon this simple binary foundation of benefit versus harm.

This completes the set of tentative definitions and hypotheses that will serve as our platform for heuristic construction of a theory. Now, let's build a brain!

Back to Reality, Dimensions and the Natural Ontology || On to Motivation in Natural and Artificial Systems

This series begins with The Machine in the Ghost