Halliday & Matthiessen (1999: 429):
… for us [Fawcett's extralinguistic] “knowledge of the universe” is construed as meaning rather than as knowledge. This meaning is in the first instance created in language; but we have noted that meaning is created in other semiotic systems as well, both other social-semiotic systems and other semiotic systems such as perception. Our account gives language more of a central integrative rôle in the overall system. It is the one semiotic system which is able to construe meanings from semiotic systems in general.