It is widely accepted that it counts for a metaphysical theory when the theory is in accord with common sense and against a metaphysical theory when the theory clashes with common sense. It is unclear, however, why this should be the case. When engaging in metaphysics, why should we give common sense any weight? This chapter maintains that it is only against the backdrop of a particular metametaphysical stance that questions about metaphysical best practices become tractable. From the perspective of a metaphysics-as-modelling approach, common sense ought to play a significant, though defeasible, role in metaphysical theorizing. According with common sense is one of a number of theoretical virtues that metaphysicians should strive for. Nevertheless, it is important for the metaphysician to be cautious when appealing to common sense. She should distinguish what actually falls within the bounds of common sense as such from what a particular researcher happens to find intuitive. Furthermore, our best scientific theories may undercut the evidence provided by common sense. Finally, the metaphysician should attend to the context in which she invokes common sense. For some topics of inquiry, common sense ought to play a more expansive role in our metaphysical theorizing than for others.

The discoveries of the new science of the sixteenth and seventeenth centuries offered unique challenges to philosophers concerned with answering scepticism or with defending common-sense beliefs. This chapter focuses on how Descartes, Locke, and Berkeley took up those challenges. Descartes’s philosophical project brought to the forefront the tensions embedded in the confrontation between common sense, science, and scepticism. His insistence on raising the strongest sceptical doubts and on answering them with absolute certainty often left common-sense beliefs behind. Confronted with this result, and perhaps also with Descartes’s own failure to answer the sceptic, Locke weakened both the force of his own scepticism and the degree of certainty he demanded in his philosophical views. Moreover, he was often willing to privilege common-sense beliefs over arguments conflicting with them. In these ways, he provided a system which reconciled common sense, science, and scepticism more adequately than Descartes. Berkeley, convinced that his predecessors’ work left the sceptic unscathed, developed views which, he claimed, completed this reconciliation project. But the chapter shows that his views fall short of this goal. The work of these philosophers put in place the foundations upon which later thinkers would tackle this reconciliation challenge.