Nicholas of Cusa on ET life and earth's motion

by Salman Hameed

I am co-teaching Astrobiology this semester. Last week we looked at the idea of extraterrestrial life from antiquity through the Scientific revolution. One of the figures that stood out for me was Nicholas of Cusa (1401-1464) - a fifteenth century German philosopher, theologian and mathematician. In fact, not only did he talk about extraterrestrial inhabitants, he also took motion of the Earth for granted - a 100 years before Copernicus's book on heliocentrism. Sure enough, Nicholas of Cusa was not basing his ideas on any observations or on a cosmological system, but still, it is fascinating that he wrote this in his book, Of Learned Ignorance (as quoted in Crowe's The Extraterrestrial Life Debate):

The ancient philosophers did not reach these truths we have just stated, because they lacked learned ignorance. It is now evident that this earth really moves though to us it seems stationary. In fact, it is only by reference to something fixed that we detect the movement of anything. How would a person know that a ship was in movement, if, from the ship in the middle of the river, the banks were invisible to him and he was ignorant of the fact that water flows? Therein we have the reason why every man, whether he be on earth, in the sun or on another planet, always has the impression that all other things are in movement whilst he himself is in a sort of immovable centre; he will certainly always choose poles which will vary accordingly as his place of existence is the sun, the earth, the moon, Mars, etc. In consequence, there will be a machina mundi whose centre, so to speak, is everywhere, whose circumference is nowhere, for God is its circumference and centre and He is everywhere and nowhere.

It seems that the thinking of Giordano Bruno and Kepler was influenced by Nicholas of Cusa (see this link for the connection between Kepler and Nicholas of Cusa). By the way, this is what Thomas Kuhn had to say on this: "Nicholas of Cusa...derived the motion of the earth from the plurality of worlds in an unbounded Neoplatonic universe".

And here is Nicholas of Cusa on extraterrestrial life. While be believes that life everywhere, he does give Earth ("and its region") a bit of an advantage:

Nor can place furnish an argument for the earth's baseness. Life, as it exists here on earth in the form of men, animals and plants, is to be found, let us suppose, in a higher form in the solar and stellar regions. Rather than think that so many stars and parts of the heavens are uninhabited and that this earth of ours alone is peopled- and that with beings, perhaps, of an inferior type-we will suppose that in every region there are inhabitants, differing in nature by rank and all owing their origin to God, who is the centre and circumference of all stellar regions. Now, even if inhabitants of another kind should exist in the other stars, it seems inconceivable that, in the line of nature, anything more noble and perfect could be found than the intellectual nature that exists here on this earth and its region. The fact is that man has no longing for any other nature but desires only to be perfect in his own.

But I like his speculations about solar beings and lunatics:

For since that whole region is unknown to us, its inhabitants remain wholly unknown. To go no further than this earth:-animals of a given species unite to form a common home of the species and share the common characteristics of their habitat, knowing nothing of or caring nothing for strangers. Their idea of strangers, even if it reaches some kind of vocal expression, is wholly exterior and conjectural and, such as it is, conceivable only after lengthy experience. Of the inhabitants then of worlds other than our own we can know still less, having no standards by which to appraise them. It may be conjectured that in the area of the sun there exist solar beings, bright and enlightened intellectual denizens, and by nature more spiritual than such as may inhabit the moon-who are possibly lunatics- whilst those on earth are more gross and material. It may be supposed that those solar intelligences are highly actualized and little in potency, while the earth-denizens are much in potency and little in act, and the moon-dwellers betwixt and between.  

We make these conjectures from a consideration of the fiery nature of the sun, the water and air elements in the moon and the weighty bulk of the earth.

Fascinating stuff. On the one hand, this reminds us that the conversations over extraterrestrial life have been going on for centuries. On the other hand, this also illuminates the way medieval science was different from the way we think about this question today.