Everyone I’ve come across thus far who has written about design thinking cites Herbert Simon’s book The Sciences of the Artificial. Simon was a great thinker in economics (Nobel Prize), computer science and cognitive science. For considering the construct of design at the cognitive level, this book is part of the canon. In it he identified one aspect as what we now call abductive thinking — the mental creation of something new — as opposed to inductive or deductive thinking. A favorite quote:

“Engineering, medicine, business, architecture and painting
are concerned not with the necessary but with the contingent —
not with how things are but with how they might be —
in short, with design.”