Probability, prudence, danger: Thomas Aquinas on the building of the lexicon of risk

International audience ; The Latin terms commonly used to signify 'risk' are absent from Thomas Aquinas's economic writings. Instead, Aquinas offers a lexicon of probability, prudence and danger. This ternary lexicon brings with it a triple universalisation of risk: first, a universalisation through activity, including the activity of analysis considered as part of economic activity; second, a universalisation through the agents, since everyone-the observer, the co-contractors, the prince and the population-is affected by the risk; and, finally, a partial universalisation of its definition, since the lexicon indicates a risk which is not yet restricted by calculation, as the modern notion is, although some distinctions are already made by Aquinas. However, the lexicon only describes a risk of loss and does not take into account chance of gain.