In the hands of Petrarch and other great writers of his own and later times, the sonnet became one of the most popular forms of verse in Europe. Such popularity for any particular type of literature never arises without a reason. The aim of the sonnet is to embody one single idea or emotion, one deep thought or wave of strong feeling, to concentrate the reader's whole mind on this one central idea, and to clinch it at the end by some epigrammatic phrase which will fasten it firmly in the reader's memory. For instance, in Milton's sonnet _On his Blindness_, the central idea is the glory of patience; and the last line drives this main idea home in words so pithily adapted that they have become almost proverbial. During the sixteenth century, rich young Englishmen were in the habit of traveling in Italy for education and general culture. They brought home with them a great deal that they saw in this brilliant and highly educated country; and among other things they imported into England the Italian habit of writing sonnets. The first men who composed sonnets in English after the Italian models were two young noblemen, Sir Thomas Wyatt and the Earl of Surrey, who wrote just before Shakespeare was born. Their work called out a crowd of imitators; and in a few years the writing of sonnets became the fashion. {66} As a young man, Shakespeare found himself among a crowd of authors, with whom sonnetteering was a literary craze; and it is not surprising that he should follow the fashion. Most of these were probably composed about 1594, when the poet was thirty years old; but in regard to this there is some uncertainty. A few were certainly later. They were not printed in a complete volume until 1609;[6] and then they were issued by a piratical publisher, apparently without the author's consent. In the Shakespearean sonnet the complicated rime scheme of its Italian original has become very much simplified, being reduced to the following form: _a, b, a, b; c, d, c, d_; _e, f, e, f_; _g, g_. This is merely three four-line stanzas with alternate rimes, plus a final couplet. Such a simplified form had already been used by other English authors, from whom our poet borrowed it. Shakespeare's sonnets, apart from some scattered ones in his plays, are 154[7] in number. They are usually divided into two groups or sequences. The first sequence consists of numbers 1-126 (according to the original edition); and most of them are unquestionably addressed to a man. The second sequence contains numbers 127-154, and the majority of these are clearly written to a woman. There are a few in both groups which do not show clearly the sex of the person addressed, and also a few which are not addressed to any one. {67}