This is a brilliant work. Inventive, creative, light-written, clearly exposed to laymen, and proposing a very stimulating plan: demonstrating how, by means of the accumulation of well-defined and feasible (though not always as literally presented) mechanisms, initially trivial "vehicles" can develop emergent properties that can be defined by psychological jargon and assume the appearance of purposeful, thinking brains. A central tenet of this ascending spiral of thought experiments - which is later followed by an attempt to give physical or physiological bases to the proposals according to the (at the time of writing) up-to-date neurological and physiological knowledge - is what the author calls the "law of uphill analysis and downhill synthesis". By this, it is meant that we tend to overestimate the complexity of the underlying structures giving rise to the phenomena we observe. That is, it is much more difficult to divine the supposed structure(s) by analysis than by a synthetic approach. The book is leaving proof of this. It embodies a sort of creative reductionism akin to Schweitzer's brownian agents framework - where cumulative features give way to emergent affirmations which, in absence of such constructive proof, would tempt to be justified by much trickier assumptions.
Imaginative pictures finish this little gem of a book, recommended to all curious and disillusioned people.