The article studies the role of scholastic terminology, notably that of Suárez, in shap¬ ing a new ontology which, basing on cogito as its starting point, gains a further explica¬ tion as «the metaphysics of representation», pertaining to the Modern Age, or, accord¬ ing to Martin Heidegger, to the Age of World Picture. The primary concern of the work is the notions of «substance» and «existence» as well as their difference, defined by Suárez as «a mental distinction with a foundation in the thing itself».