Abstract: This paper starts from the skepticism of modern people since Descartes, and discusses the methodological significance of Hume's moral philosophy around the natural meaning of common life. Modern individuals seem to rely on pure reason to understand the world and search for absolute certainty, only to find things in common life suspicious and incomprehensible. Hume abandoned the mathematical model used by Descartes and his successors, and instead chose a daily life perspective to conduct experiments. He found that men were mightily governed by imagination and passion rather than their cogitative rationality. This allows them to live in an environment of precedents and customs in an interconnected manner. If modern men each adhered to their own ideal standards set by false reason, consensus and compromise could hardly be achieved. Hume believed that moral philosophy had its own objectives and methods that were very different from natural philosophy's search for universal laws through mathematical models. It shouldn't try to attain perfect precision and exactness that human nature could never attain. Its goal was to promote moderation rather than produce extreme. By revisiting Hume's moral science, this paper attempts to reflect on sociology's pursuit of quantitative scientific models, and explore how to go beyond the "limited understanding" of the society offered by natural science and truly penetrate into the operation of moral factors such as ideas, customs and common beliefs in people's daily life, which are often the real basis for social interactions and dealings.

Key words: common life, Nature, law of association of ideas, moral philosophy