Well I asked. Luke Wroblewski posts a helpful guide to a number of recent thoughts on design thinking, "Defining Design Thinking." Abductive reasoning and the world discovered from "from the inside" figure prominently.
Of the sources listed, Luke's description of Roger Martin's Design of Business resonates: "The style of thinking in traditional firms is largely inductive – proving that something actually operates – and deductive – proving that something must be. Abductive reasoning suggests "that something may be, and [reaches] out to explore it."
Daniel Pink's six "high-concept, high-touch" skills - design, story, symphony, empathy, play, meaning - are also mentioned. Design, as Pink says in this HowDesign.com interview linked to by Functioning Form, persuades through narrative. Narrative is logic or reason contextualized, which means an ability to see the world from the inside is indispensable.
Last August, Luke produced a table outlining the differences between design and business thinking that I've referred to often. Good stuff.