On a cultural level, the Italian Renaissance lifted Europe into a new era of humanism that glorified humanity and shifted attention to the present needs and desires of people. Erasmus translated this humanistic attitude into scholarly pursuits that revealed the frailties and needs of the human authors of Scripture. All of these forces eroded the authority of the Church, leading to dramatic confrontation, both from inside and outside the Church. The Protestant Reformation took advantage of the rift between Christian monarchs and the papacy, successfully fragmenting the unity of Western Christendom. However, it was Copernicus who used the strategy and tools of reasoned arguments to arrive at his heliocentric theory of planetary motion. This bold assertion successfully demonstrated a truth arrived at through reason that differed from the conclusion supported by the authority of the Church. As a result, reason triumphed over faith, and the age of science began. While psychology remained obscured within philosophy and religion during this time, the enduring questions still perplexed scholars and were about to be addressed directly over two centuries of philosophical inquiries prior to psychology’s formal definition as a distinct science.

Many have difficulties understanding what Kuhn meant when he spoke of “world change” due to revolutions. I reconstruct the historical path in which the idea emerged that reality is not something purely object-sided. The path starts with Copernicus’ new planetary system. The motions of the Sun and the planets, previously seen as purely object-sided, were now seen as containing genetically subject-sided contributions. A similar process, also at the center of the constitution of modern science, was the introduction of secondary qualities in the seventeenth century. In these historical processes, the reality status of something, whose reality seemed beyond doubt, changed dramatically. Philosophical reflection of such processes culminates in Kant’s critical philosophy. Ever since, this kind of “post-Copernican thinking” has been an indispensable part of the Western intellectual tradition, and it surfaced in the development of special relativity and quantum mechanics. I argue that Kuhn is continuing this tradition. Understanding this genealogy may make Kuhn’s metaphysics accessible to those realists who maintain that talk of genetically subject-sided contributions to reality is utterly inconsistent.

I argue historical information on the relationship between Copernicus’s work and Islamicate astronomy, which came to light when Kuhn was writing The Copernican Revolution, complicates the depiction of Copernicus’s work as revolutionary, or discontinuous with previous astronomy. I consider Saliba’s claim that Tusi’s work was “a Scientific Revolution before the Renaissance.” I conclude that, although Tusi’s work is important, it is better understood as extending normal science. Similar arguments undermine the claim that Copernicus’s work was revolutionary. Earlier histories of the Copernican revolution have given too little credit to the innovations of Tycho Brahe, and his imitators and opponents, and the solid scientific reasons for preferring Tycho’s system over Copernicus’s as late as 1650. However, the situation in European astronomy and cosmology from the career of Copernicus to the death of Newton does look like a Kuhnian crisis state. It is also possible to locate incommensurabilities between heliocentric and geocentric cosmologies, especially beginning with Kepler. The concept of incommensurability remains an important resource for understanding the history of science.

The birth of physics can be traced to the Copernican, Galilean and Newtonian revolutions of the seventeenth century. The Copernican picture of the world was to replace the geocentric Ptolemaic model. Tycho Brahe's innovations in observation brought about an order of magnitude improvement in the determination of the motions of the planets. These observations resulted in the formulation of Kepler's laws of planetary motion, which were to be crucial in Newton's discovery of the laws of motion.At the same time, Galileo's pioneering telescopic discoveries provided support for the Copernican picture of the world.