Mark Johnson: "Philosophy's Debt to Metaphor" (2008)

Just a couple of quotes from Johnson's contribution to the Cambridge Handbook of Metaphor and Thought (2008):

Conceptual metaphor is a structure of human understanding, and the source domains of the metaphors come from our bodily, sensory-motor experience, which becomes the basis for abstract conceptualization and reasoning. From this perspective, truth is a matter of how our body-based understanding of a sentence fits, or fails to fit, our body-based understanding of a situation. (p. 45)

Indeed, once you make the links, no specific training is needed:

All theories are based on metaphors because all our abstract concepts are metaphorically defined. Understanding the constitutive metaphors allows you to grasp the logic and entailments of the theory. (p. 51; emphasis in original)

Further, we should recognize the "the crucial role of metaphor in shaping and constraining inference in ordinary mundane thinking" and "the pervasive workings of conceptual metaphor in shaping our conceptual systems" (both p. 28). We are also told that "conceptual metaphors lie at the heart of our abstract conceptualization and reasoning" (p. 51).

Also, "metaphors are based on experiential correlations and not on similarities" (p. 46).