 From the beginning of his career to the end, Mendelssohn consistently upheld the demonstrability of God’s existence. However, not all arguments were equally compelling in his view. In the Prize Essay he contends that probable arguments for God’s existence based upon beauty, order, and design are more eloquent and edifying but less certain and convincing than strict demonstrations. Similarly, in Morning Hours, he cites the argument that the external senses’ testimony to an external world is unthinkable without a necessary, extra-worldly being, but adds that this sort of argument would hardly convince an idealist, sceptic, or solipsist. There are, however, at least two ways in which, according to Mendelssohn, God’s existence can be established with certainty. The first way is through application of the principle of sufficient reason to the certain existence of contingent things. The inner testimony of one’s own cogito attests to the existence of something contingent. Since the sufficient reason for the existence of contingent things must “indirectly” be a necessary being, a necessary being exists. Hence, Mendelssohn sums up this argument by saying: “I am, therefore there is a God.” (Philosophical Writings, p. 289; Gesammelte Schriften, 3/2, pp. 78, 83f).