This expression is about the InterTwingled relationship between the domains of Concepts, Symbols, and their Referrents.

I think you mean the SemioticTriangle: http://en.wikipedia.org/wiki/Semiotic_triangle

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Some say the notion comes from I. A. Richards, as his description of the relationship between words, thoughts and things. Though just what the difference is between thoughts and things is kind of the problem we're trying to address in the first place ...

''That's a FrameProblem. There can be no distinct things - only the undistinguished Tao (WhatIsTao) - except as things are represented empirically (symbolically). See LeibnizianDefinitionOfConsciousness for more on same.''