Depending on the edition, the twenty-fifth or twenty-sixth quatrain of Edward FitzGerald's translation of The Rubáiyát of Omar Khayyám reads,
Why, all the Saints and Sages who discuss'd
Of the Two Worlds so wisely—they are thrust
Like foolish Prophets forth; their Words to Scorn
Are scatter'd, and their Mouths are stopt with Dust.
The topic of discussion for both the sages and the saints, the wise men and the good men, was, therefore "the Two Worlds." FitzGerald does not elaborate, but it is fairly clear in context that this means earth and heaven, this world and the next. This means that the topics covered can be very wide indeed, encompassing all things, known and unknown.
The discussions of the saints and sages, however, have not done them any good. They are just as certain to die as foolish prophets, and their words are no more likely to be revered. It is such sentiments as this that make The Rubáiyát of Omar Khayyám not merely an agnostic poem, but a nihilistic one. The poet is always telling the reader that it does not matter how good or wise you are, how much you learn, or what you may think you have accomplished: it will all come to nothing in the end. This nihilism is closely associated with hedonism: if nothing matters, you may as well do what you like. In any case, the poet sees little point in being a sage.