Abstract: This article traces the fate of the project formulated by Edmund Husserl in headline of the article “Philosophy as a Rigorous Science”. As demonstrated in the correspondence with Gustav Shpet, scientific rigor is understood as a synonym to rationality in a general sense. Following Husserl, Martin Heidegger in 1927 also speaks of the identity of philosophy and science in its original Greek sounding. It would seem that within such meaning of scientific rigor, this reasoning sounds like pleonasm. However, in fact, identification requires not only broadening of the concept of science, but also narrowing down the boundaries of mind to the limits of science. Thus becomes the question: whether or not the prerequisite of scientific rigor, regardless of the broad understanding of the latter, contradicts the underlying phenomenology principle of non-prerequisite. In such case, phenomenology, in order to remain faithful to the “things themselves”, must overcome the horizon of the rooted in classical rationalism project of structuring philosophy as a rigorous science. Heidegger makes this step back in 1929, claiming that transformation into the absolute science is not the capability of philosophy whatsoever. Husserl, in turn, if judging by the published during his lifetime works, remains faithful to his idea to the end. Nevertheless, some fragments out of the published postmortem, give cause for making a careful assumption that at the close of his days comes to realization of unfeasibility of his own aspirations. Hence, the downfall of the project of philosophy as a rigorous science not in the slightest degree means the crash of phenomenology as such, but rather is a decisive step that allows the latter gaining faithfulness to its fundamental principles.