Generally, Descartes is considered a philosopher who played a significant role in the foundation of modern philosophy and is also regarded as the one who paved the way for scientific thinking. Among Descartes' views, his attention to mathematics as a science that entirely contains "certain propositions" is prominent. This attention made him believe in the theory of the unity of sciences with mathematical characteristics. From Descartes' point of view, "measurability," "order," and " deductive method" are the main features of mathematics. He used the term "universal mathematics" for all sciences that benefit from those characteristics. Among his opinions, Descartes' understanding of "infinity" is also different from most scholastic philosophers. He considered infinity as a positive concept that exists in humans and contrasts with the conventional perception; he believed that it is possible to have a perception of the finite from the rejection of the infinite. However, this attitude has faced many challenges up to now. In this article, we will investigate Descartes' theory of infinity and demonstrate that his work was a good start but encompassed theoretical ambiguities that later have been clarified by mathematicians.