1 - Bruno's Crusade Against Medieval Aristotelianism

Giordano Bruno was a fervent defender of Neo-Platonism against the rationalist and empirical ideas of Aristotle. Bruno opposed his natural philosophy and knowledge via the senses, desperately trying to prove the absurdity expressed within. Bruno shocked the thinkers of the era, who were still under the yoke of a universal thought in conformity with the Christian idea, and was quick to refute the Aristotelian conception of a closed world, even though the Church drew its explanation of the faith from this conception and did not tolerate any deviation from the idea. It should not be forgotten that this was a time when anything with a non-Aristotelian outlook or tending to contradict the Aristotelian philosophy was immediately branded heretical.

Bruno stubbornly and audaciously went on the attack, arguing that "he who denies the infinite effect denies the infinite power".

While Copernicus announced his theory of heliocentrism, according to which the celestial spheres, including the Earth, revolved around the sun, taken as the centre of the universe, Bruno went even further. The philosopher acknowledged the movement of the Earth, though whereas Copernicus spoke of the sphere of fixed stars as being an unchanging and static element, Bruno explained that it was an illusion created by the rotation of our planet.

Consequently, he refuted the idea of a finite cosmology, to which Copernicus continued to adhere, and presented his conception of an infinite universe. In a way, he removed any remaining Aristotelian influence from Copernicus's theories and pushed heliocentrism as far as the idea of infinite worlds where man was not exclusive.

He also countered Christian geocentrism, which placed man in the centre of the Universe, with an audacious relativism for his time: "there is no top or bottom, no absolute positioning in space. There are only positions that are relative to the others. There is an incessant change in the relative positions throughout the universe and the observer is always at the centre".

In respect of his theory on infinite worlds, Bruno added the idea that nature was governed by sprits. According to him, every thing, object, animate or inanimate element was equipped with a soul: "there is no reality that is not accompanied by a spirit and an intelligence".

Bruno opposed Aristotle's determinism and the Catholic conception by explaining that the soul was an active and internal principle ensuring harmony and that "it is the soul that governs, moves, gives life, maintains and contains". In On Cause, Principle and Unity, he added his idea of unity: "the soul of man and the soul of beasts are but one, they only differ by their exterior dispositions". This soul, which is identical and present in any every vital or non-vital element, is the soul of the world that possesses its own intellect and appears as the principle of nature.

Against the Aristotelian idea that matter can be divided until it loses its reality, Bruno put forward the argument according to which "the infinite world implies the existence of matter made up of indivisible atoms".

But that is not all. Jacques Attali saw him as a true pioneer of atomism, the ancestor of Mendeleïev and a visionary of genetic science after reading what Bruno wrote in 1590: "there does not need to be several sorts and forms of tiny elements, furthermore nor letters to form innumerable species".