 Why think that fundamental entities must be homogeneous (as per 17)? Here are the best two (related) attempts one might make at defending 17. First attempt: nothing can differ from itself. For a fundamental entity to be heterogeneous would be for it to be internally diverse, which would render it different from  itself.[50] Second attempt: the priority pluralist has a way of accounting for heterogeneity that the monist lacks. The pluralist has many fundamental entities, which may all be homogeneous, but might still be different from each other. Hence if the only way to account for heterogeneity were to have many fundamental homogeneous parts differing from each other, then the priority pluralist would have the only way to account for heterogeneity. Perhaps this line of thought is behind the following passage from Turner (1911):