This text analyzes the philosophical relationship between the subject and its counterpart within the context of human action. The author argues that active engagement requires not only a subject as the center of activity but also something toward which that action is directed. This counterpart is not necessarily a mere inanimate object or thing; it is frequently another subject or a group of subjects. The text critically reflects on the foundations of modern European thought, specifically the Cartesian dualism of thinking things and extended things. Descartes perceived thinking as a substance rather than an activity of a subject in the modern sense. Consequently, his conception viewed the external world and other living beings primarily as machines or objects rather than true counterparts. This abstract highlights the ontological distinction between a passive object and an active subject, illustrating how historical definitions of substance have shaped modern conceptions of intersubjectivity and our relationship to the other.