The text tries to answer the question of the sources of misunderstandings connected with the reception of Spinoza’s philosophy, especially with his understanding of the substance, attributes, modifications and infinity in Ethics. Assumptions made by Spinoza, for instance the postulate of describing the human being as a „state in a state” of Nature during a research procedure comply with the rules of model of the modern science. In Ethics, based on The Elements by Euclid, the author presents the attempt to define the basic terms used by the philosophers and scholars of the XVIIth century, and, on this basis and taking axioms into account, he works out a number of theorems concerning Nature, including the nature of a human being. Euclid’s Elements served as a template of the construction of a theory, which in a logically necessary manner, precisely and at the same time „suspending” the interference of destructive human emotions, proves the properties of the objects of geometry. Spinoza tried to establish a theory which would examine the properties of human mind and body treated as a subject of science (geometry and physics as far as body is concerned, psychology and ethics in case of the mind) in an equally rational, precise and motionless matter, starting from the basic definitions. Its basics became, among others, definitions of substance, attribute and modification, inspired by the Aristotelian-Scholastic tradition. Those terms, interpreted in Christian Europe through the teachings of the Old and New Testament, have taken a completely different character and meaning in Ethics. Upon encountering the text of definitions and theorems the readers were unable and, quite often, unwilling to resist the temptation of adding their own beliefs to the contents. This article treats of this conflict of language and beliefs.