Knowledge is information stored in the mind and in human artifacts like stories, books, and internetworked computers. Knowledge is information that forms the basis for human thoughts and actions. Among these are theories and experiments of scientists, who collaborate to establish our knowledge of the external world.

Information is stored or encoded in structures. Structures in the world build themselves, following natural laws, including physical and biological laws. Structures in the mind are partly built by biological processes and partly built by human intelligence, which is free, creative, and unpredictable.

To the extent of the correspondence, the isomorphism, the one-to-one mapping, between structures (and processes) in the world and representative structures in the mind, we claim to have knowledge of the world.

When information is stored in any structure, two fundamental physical processes occur. First is a collapse of a quantum mechanical wave function. Second is a local decrease in the entropy corresponding to the increase in information. Entropy greater than that must be transferred away to satisfy the second law.

These quantum level processes are susceptible to noise. Information stored may have errors. When information is retrieved, it is again susceptible to noise, This may garble the information content. In information science, noise is generally the enemy of information. But some noise is the friend of freedom, since it is the source of novelty, of creativity and invention, and of variation in the biological gene pool.

Biological systems have maintained and increased their invariant information content over billions of generations. Humans increase our knowledge of the external world, despite logical, mathematical, and physical uncertainty. Both do it in the face of noise. Both do it with sophisticated error detection and correction schemes. The scheme we use to correct human knowledge is science, a combination of freely invented theories and adequately determined experiments.