The contemporary discussion of artificial intelligence is not the first time human beings have wrestled with the possibility of other minds that are not human minds. Scholastic philosophers invested a considerable effort into understanding angels, with angels understood to be higher than human beings on the great chain of being. And the links of the great chain of being represent fundamentally different kinds of things that jointly constitute the world, and not a gradual ladder of progress, which is how it is often interpreted today.
A significant chunk of Saint Thomas’ Summa Theologiae is devoted to angelology: Questions 50 through 64 is the “Treatise on Angels,” which goes into a luxury of detail in relation to the nature of angels. In the Bible, angels interact with human beings, but human beings are not the same kind of beings as angels, so this poses certain problems. Aquinas (and other Scholastics) takes the bull by the horns and wrestles directly with these problems posed by angels. Since angels do not need to breathe or drink or eat, which human beings must, there are questions that must be answered about, for example, what was going on when Lot invited two angels to his house in Sodom and he prepared them a meal.
While these questions are interesting, much more interesting are the questions about the minds of angels — how they think, what they know, and how they know. Aquinas argues (First Part, Question: 54, Article: 5), citing Averroes to underline his argument, that angels are only intellect and will (and, by implication, that the angelic mind has no component of sensation) because they have no bodies naturally joined to them:
“…In our soul there are certain powers whose operations are exercised by corporeal organs; such powers are acts of sundry parts of the body, as sight of the eye, and hearing of the ear. There are some other powers of the soul whose operations are not performed through bodily organs, as intellect and will: these are not acts of any parts of the body. Now the angels have no bodies naturally joined to them, as is manifest from what has been said already (Question , Article ). Hence of the soul’s powers only intellect and will can belong to them.” “The Commentator (Metaph. xii) says the same thing, namely, that the separated substances are divided into intellect and will. And it is in keeping with the order of the universe for the highest intellectual creature to be entirely intelligent; and not in part, as is our soul. For this reason the angels are called ‘intellects’ and ‘minds,’ as was said above (Article , ad 1).”
For the contemporary reader coming from the mainstream of naturalistic Anglo-American analytical philosophy (meaning more-or-less my own philosophical perspective), the Thomist Treatise on Angels is a thought experiment that takes as its premise, “If there are beings such as this, what will the properties of these beings be?” When we today contemplate the possibility of strong AI (or, what I consider more interesting, machine consciousness), we are similarly asking, “If there are beings such as this, i.e., minds attributable to machines, what will these minds be like? How will they think? What will be their motives?”
Would we say that machine minds have no corporeal bodies naturally joined to them, or would we say that the machine itself would be the corporeal body of some artificial intelligence? One of the persistent ideas about artificial intelligence is that this would be very different from human minds because of the lack of embodiment, and Aquinas seems to point to angels being very different from human beings not merely because they lack corporeal bodies, but because their lack of corporeal bodies means that the angelic mind is distinct from the human mind.
One question that vexes artificial intelligence researchers, and especially those who speculate on superintelligence, is the orthogonality problem (the problems that arise from the orthogonality thesis, viz. that final goals and intelligence levels are independent). This problem does not exist for angelology, as we can be assured, ab initio, that the motivations of human beings and angels, along with all the rest of creation, are aligned with divine purpose, so that there cannot be a radical departure from the directionality to history imposed by an omniscient, omnipresent, and omnipotent deity.
Now, it is true that rebellious human wills defied divine purpose, and indeed Satan defied divine purpose, but the universe is still unfolding according to the divine plan, despite these misbehaviors. To pursue this would take us deep into the theological permutation of the freewill/determinism debate (which, significantly, is not how the problem is posed or debated today), so we must be content with the idea that the Lord works in mysterious ways and leave it at that.
In place of the theological framework within which our ancestors grappled with the problems of non-human minds, we have a naturalistic and scientific framework within which we think about the minds of machines, the minds of ETI, and the minds of our own species in the distant past and in the far future. In this naturalistic framework there are forms of directionality (though not that of a divine will) with which all existents must align, and by this I mean that arrows of time as they have been variously defined and distinguished.
Different lists of arrows of time have been produced, all of which I have seen include the thermodynamic arrow of time, which thus points to some consensus. I consider the increasing metallicity of the visible universe to be as robust as the thermodynamic arrow of time, though I have not seen it any of these lists of arrows of time. However you choose to parse the irreversibility of the cosmos, if you recognize arrows of time that introduce irreversibility into the world, then this is a minimal naturalistic alignment that will hold for all minds, whether human, animal, ETI, machine, or otherwise. In other words, any or all of these minds would be minimally subject to the irreversibility of the arrow(s) of time.
As I said, this is a minimal naturalistic alignment. I strongly suspect that an analysis of consciousness would reveal structures of consciousness that any consciousness would have in common with any other consciousness, and that would mean that there would be some structures of consciousness in common, as well as some structures only shared by a smaller subset of conscious agents. However, as I noted in Must a Philosophy of Mind be a Philosophy of Consciousness? and Extended Cognition and Naturalism, if a philosophy of mind is not also a philosophy of consciousness, we may have to treat the problems of mind and consciousness separately.
If we do so, identifying a mind-body problem distinct from a consciousness-body problem, this distinction gives us a minimal framework for understanding machine intelligence that is not also machine consciousness (and, I suppose, vice versa). And there are some potential advantages to making this distinction. While the idea of extended cognition as applied to human beings or other biologically implemented minds seems, at times, a bit of a stretch, I would not hesitate nearly so much in attributing extended cognition to a machine mind. Every component that we plugged into a machine mind, or which we networked with a machine mind, would constitute a kind of extended cognition.
Here we might get into philosophical problems unique to a machine mind that do no (at least, do not yet) apply to biologically implemented minds. For example, where would we draw the distinction between a machine mind proper and its extended cognition? If we plug a new module into a machine mind, is this simply a larger machine mind, or is it a machine mind with extended cognition? And there would be problems of a sorites paradox involved in making a machine mind larger or smaller: how many components can we take away from a machine mind and have it still be a mind?