It is widely believed that the eighteenth century is the pinnacle of rationalism and rationality in history. In particular, Immanuel Kant is seen as the most representative philosopher of eighteenth-century German rationalism. Without going into much detail about Kant, this chapter takes a closer look at the prerequisites for the intellectual and cultural upheavals that took place before Kant. In this context, the entry of psychology into philosophy is examined more closely in this chapter. The methodological approach is based on a cultural-historical approach that leads to a focused examination of how psychology could be defined as a clear and delimited field. In this chapter, the focus is particularly on Alexander Baumgarten. The reason for this is that he was a key premise setter for how psychology was understood in the eighteenth century. In addition, he is considered the most important contributor to the shaping of modern aesthetics. Hence, the main purpose is to show the original connection between the two disciplines of aesthetics and psychology. What is being revealed is consequently unfolding on two levels. One is at the cultural and societal level, where we see tendencies towards major political and societal upheavals in some parts of Europe, where the main focus of these changes is an emphasis on individuality through greater participation by the individual citizen. At the same time, there is an increased interest in our senses in the form of being able to enjoy different aspects of life, such as literature, music, food, and entertainment. The second level is the intellectual, where the senses also became a crucial factor. Sensation was seen as an absolute prerequisite for being able to attain true knowledge. Based on this, Christian Wolff incorporates psychology into metaphysics. But with him, rationality comes at the expense of sensation. Hence, Alexander Baumgarten truly unites rationality with sensation without upsetting the balance between them. This is why he also launches the neologism “aestheticology.”