Infinite Minds is the fourth book of John Leslie, which follows Value and Existence (1979), Universes (1989) and The End of the World (1996). Infinite Minds presents a very rich content, and covers a number of particularly varied subjects. Among these latter, one can notably mention: omniscience, the problem of Evil, the fine-tuning argument, observational selection effects, the identity of indiscernables, time, infiniteness, the nature of consciousness.
The book places itself clearly within the field of speculative philosophy. And Leslie is primarily concerned here with considerations not of rigorous demonstration, but rather of plausibility and of coherence. He thus does not hesitate sometimes to attribute a rather weak probability to certain assertions.
Some readers may be rebutted from the beginning by the counter-intuitive assertion that galaxies, planets, animals, but also each of us and our surrounding objects, are mere structures among divine thoughts. One can think that such an assertion has motivated the commentary placed on the book’s cover by a reader from Oxford University Press, according to which it may be difficult to believe that the universe is such that the author describes it. This was also my primary reaction. But if certain readers were to draw from that a hasty conclusion, they would miss then, I think, what constitutes the hidden treasure of the book. Because Infinite Minds resembles a sumptuous temple, whose access however is dissimulated by a gate which looks poorly attractive. Those who will not cross the door, rebutted by the aspect of this latter, will not have the occasion to contemplate the hidden treasures that the book contains. Because the book presents an overall deep structure and coherence, based on the consistency of the author’s pantheist conception of the universe with our current most advanced scientific views with regard to cosmology, physics, as well as with the solutions to several contemporary philosophical problems. To show synthetically how a pantheist vision of the world can cohere with our most recent views with regard to multiple universes, physics and quantum computer science, inasmuch as with relativity theory and recent discussions relating to omniscience, the problem of Evil, the fine-tuning argument, observational selection effects, etc. appears both an immense and deeply original task.
It should be observed here that Leslie is familiar with this type of wide-scale work. It suffices for that to consider his whole work relating to the Doomsday Argument. It is worth evaluating here the immense task which consists in defending point by point the Doomsday Argument against a good hundred different objections. But this vigorous defense of the Doomsday argument has stimulated in return the development of a rich literature, which continuously enlightens a number of fields hitherto ignored.
The variety of pantheism described by Leslie, inspired by Spinoza, characterizes itself by the fact that each of us is nothing but a structure of divine thoughts. Because the divine mind only exists. The galaxies, the planets, the mountains, the human beings that we are, the animals, the flowers are nothing but structures within divine minds. As Leslie points out, this is coherent with the way physicists themselves describe physical objects, by specifying their intrinsic properties. Nevertheless, Leslie is not committed to a conception of panpsychism where all beings and objects which are part of our universe, have mental properties. For according to the author, physical objects such as trees, rocks, sand, exist as structures within the divine mind, but without being equipped themselves with conscience or thought. Here, all things are not equipped with conscience, but are such however that a conscience of these latter things exists.
Moreover, universes in infinite number can exist as structures in the divine mind. The author’s theory appears thus compatible with recent cosmological theories based on the existence of multiple universes. One of these universes is thus our own, which presents such characteristics and an accurate tuning of its parameters (the ratio of the respective masses of the electron and proton, the electron charge, the gravitational constant, Planck’s constant, etc.), that it allows the emergence of an intelligent life.
Furthermore, Leslie suggests the existence not of a single divine mind, but as well of an infinity of divine minds. Each of them is absolutely identical to the others, but has however an autonomous conscience of its own existence.
What is then the status of abstract objects, such as natural integers, in this context? According to certain philosophers, abstract objects also constitute divine thoughts. Such is in particular the viewpoint put forth by Alvin Plantinga, according to which natural integers constitute divine thoughts. But Leslie adopts a different line of thought. Abstract objects such as natural integers have in Infinite Minds’ ontology a completely original status, which is not prima facie obvious, and which deserves a detailed mention. Abstract objects such as natural integers, the idea of an apple, or the idea that “2 + 2 = 4”, are of Platonic essence. And Leslie points out that such abstract objects do not result from our brains, which themselves constitute thoughts in the divine mind. Neither do such objects of Platonic nature result from the divine mind itself. The natural integers, the idea of an apple, or the idea that “2 + 2 = 4”, constitute eternal realities, which are independent of our existence as human beings, of our thoughts and of our language. Leslie explains clearly how the idea that “2 + 2 = 4”, i.e. the fact that “IF two sets of two apples exist, THEN four apples exist” (p. 160) constitutes a Platonic reality, independent of the thoughts of the divine mind and of the human beings that we are.
Leslie also develops the topic of omniscience. According to Leslie, God simply knows all that is worth knowning: (“God knows everything worth knowing”). This seems probably more plausible than the idea according to which God has any knowledge, which notably conflicts with the logically impossible existence, already noted by Patrick Grim, of the set which contains absolutely all truths. Our pretheoretical conception of an omniscient God could well appear naïve, as the author points out, because a many unimportant facts could appear undesirable knowledge there.
Lastly, Leslie develops the point of view according to which God exists by ethical need (“because of its ethical requiredness”). The existence of God and of the cosmos in his entirety is ethically necessary, from all eternity. This argument could well appear more convincing than certain ontological arguments. Because such an ethical need has, according to Leslie, an inherently creative power. But such creative capacity, of Platonic essence, does not proceed of any external cause. It is simply inherent by nature to the ethical necessity.
Leslie’s book also constitutes the courageous expression of a viewpoint. For such pantheist conception does not constitute a widespread opinion within contemporary analytical philosophy. Moreover, Leslie’s variety of pantheism also constitutes a variation of panpsychism. But the attitude of the author appears eminently constructive, because it constrains us to consider more attentively some doctrines than we would tend to reject too easily. One will or not adhere to the pantheist and panpsychist theory exposed in Infinite Minds. But for the majority of readers for whom we can suppose that they will not adhere to the variation of panpsychism thus described, Leslie’s work constitutes nevertheless an admirable and highly original synthesis, showing how an astonishing construction can be elaborated around the pantheist model, while bringing answers to many contemporary philosophical problems. The work will provide new arguments to the defenders of panpsychism. But Infinite Minds will be also prove to be essential to the detractors of panpsychism, who will find there a particularly strong and structured defense.
1This review only differs from the version published in Philosophiques with regard to the status of abstract objects. I thank John Leslie for very useful discussion on this topic.