So hard a student was Dante that he now for a time nearly lost the use of his eyes.[58] But he was cured by regimen, and came to see as well as ever, he tells us; which we can easily believe was very well indeed. For his work, as he planned it out, he needed all his powers. The _Convito_, for example, was designed to admit of a full treatment of all that concerns philosophy. It marks an earlier stage of his intellectual and spiritual life than does the opening of the _Inferno_. In it we have the fruit of the years during which he was wandering astray from his early ideal, misled by what he afterwards came to count as a vain and profitless curiosity. Most of its contents, as we have it,[59] are only indirectly interesting. It is impossible for most people to care for discussions, conducted with all the nicety of scholastic definition, on such subjects as the system of the universe as it was evolved out of the brains of philosophers; the subject-matter of knowledge; and how we know. But there is one section of it possessed of a very special interest, the Fourth, in which he treats of the nature of nobility. This he affirms to be independent of wealth or ancestry, and he finds every one to be noble who practises the virtues proper to his time of life. 'None of the Uberti of Florence or the Visconti of Milan can say he is noble because belonging to such or such a race; for the Divine seed is sown not in a family but in the individual man.' This amounts, it must be admitted, to no more than saying that high birth is one thing, and nobility of character another; but it is significant of what were the current opinions, that Dante should be at such pains to distinguish between the two qualities. The canzone which supplies the text for the treatise closes with a picture of the noble soul at every stage of life, to which Chaucer may well have been indebted for his description of the true gentleman:[60]--'The soul that is adorned by this grace does not keep it hid, but from the day when soul is wed to body shows it forth even until death. In early life she is modest, obedient, and gentle, investing the outward form and all its members with a gracious beauty: in youth she is temperate and strong, full of love and courteous ways, delighting in loyal deeds: in mature age she is prudent, and just, and apt to liberality, rejoicing to hear of others' good. Then in the fourth stage of life she is married again to God,[61] and contemplates her approaching end with thankfulness for all the past.'[62]