Philo Judaeus De Posteritate Caini 13

[13] These suggestions and such as these are what he gives to the rest of the world, but he himself so insatiably desires to behold him, and to be beheld by him, that he supplicates him to display to his eye his nature of which it is impossible to form a conjecture, so that he may become acquainted with it, ¹ that thus he might receive a most well-grounded certainty of knowledge that could not be mistaken, in exchange for uncertain doubts; and he will never cease from urging his desire, but even, though he is aware that he desires a matter which is difficult of attainment, or rather which is wholly unattainable, he still strives on, in no way remitting his intense anxiety, but without admitting any excuse, or any hesitation, or vacillation; using all the means in his power to gain his object.