模态逻辑命题的限制条件,建立在其内容的肯定或否定其可能性,不可能性,偶然性或必然性基础之上 The classification of propositions on the basis of whether they assert or deny the possibility, impossibility, contingency, or necessity of their content.
偶然性取决于机会的情形;不确定性 The condition of being dependent on chance; uncertainty.