
Research into decision making is a most important issue today in behavioral science. Individuals are organisms yearning to exist and constantly making innumerable judgments and decisions, consciously or unconsciously. This research proposes to compare Spinoza’s behavioral theory “Ethics” with modern research findings, presented by Nobel-prize winners Tversky and Kahneman in “Thinking, Fast and Slow” and “Judgment under Uncertainty”. “Representativeness” and “Availability” as error causes of Tversky and Kahneman’s System 1 are parallel to Spinoza’s Kind I – "Inadequate cognition". For Spinoza’s Kind II - "Adequate cognition", modern research finds a solution in System 2 - slow and logical, that must constantly be refined and activated. Spinoza pioneered the systematic analysis of human behavior. His self-description from 350 years ago is endorsed by current empirical research. This research aims to present the relevance of Spinoza`s behavioral theory today.