Three Levels of Thought

Peter Gärdenfors proposes that there are three levels of abstraction for modeling thought:

Symbolic: logic, expert systems, Prolog, Cyc, good old-fashioned AI, theorem proving
Spatial: geometry, feature spaces, conceptual spaces, semantic spaces, information retrieval, vector space models, latent semantic analysis, machine learning
Connectionist: neural networks, Hebbian theory, associationism, perceptrons, neuroscience

These levels might be compared to modeling physics at [...]

The Symbol Grounding Problem

There is a view that the meaning of words (more generally, of symbols) must be grounded in sensory perception or in physical interaction with the world (embodiment). If symbols were merely defined in terms of other symbols, then it seems that we would have an infinite regression; we would spin in circles in symbol space, [...]