In the 19th century rhyming was considered a hall-mark of poetry. Novadays this artful aid is less appreciated in Europe, with the major exception of Russia, where poets are supposed to rhyme well to be worthy of their prophetic status. That is only fair because Russia is five centuries behind Europe in introduction of rhyme; it is still a relatively new toy. Others are more used to it and less smitten with it. Why should we rhyme at all? Rhyme is absent in the Bible and in the poetry of the classical period (the lines rhyme only occasionally, rather than by intent). The Greeks knew rhyme, but as a device for rhetorics rather than poetry. Milton castigated rhyme as the Invention of a barbarous Age, to set off wretched matter and lame Meeter. Dryden wrote disapprovingly that when, by inundation of the Goths and Vandals into Italy, new languages were brought in, and barbarously mingled with the Latin... a new way of poesy was practiced. In fact, rhyme is even more recent, at least in Europe. Before the 12th century, only the Irish rhymed, for reasons unknown:
...As early as the seventh century, the Irish had brought the art of rhyming verses to a high pitch of perfection... Nor are their rhymes only such as we are accustomed to, for they delighted not only in full rhymes, but also in assonances, and they often thought more of a middle rhyme than of an end rhyme. The following Latin verses, written by Aengus Mac Tipraite in 704, will give the reader an idea of the middle or interlinear rhyming which the Irish have practiced from the earliest times down to the present day:
Martinus mirus more
Ore laudavit Deum,
Puro Corde cantavit
Atque amavit Eum. http://www.newadvent.org/cathen/08116a.htm
The effect of celtic rhyming on the rest of Europe was zilch: it was a silly word game unworthy of poetry, together with writing poems in the shape of butterflies and other excesses of form. Then a book written by a canon of the church of St Victor in Paris changed it, introducing the internal rhyme into the mainstream ("En rex Edvardus, debacchans ut Leopardus"). Rhyme had its uses in Latin poetry, after all.
...The invention of rhyme is traditionally attributed to a probably apocryphal monk Leonius, who is supposed to be the author of a history of the Old Testament (Historia Sacra). This "history" is composed in Latin verses, all of which rhyme in the center. It is possible that this Leonius is the same person as Leoninus, a Benedictine musician of the twelfth century. (wiki)
Would Leonine verse become gold standard, our poets would still be flexing their brains to cast their inspiration into something like
but the fate was more merciful, because the Crusaders happened to like the sound of Persian and Arabic poetry, especially the romantic one. How starved were they for rhyme transpires from the fact that most of Arabic poetry is [in my personal opinion, crushingly monotonous] monorhyme: the same rhyme is repeated many times over. This immediately suggests its true origin, because the Chinese were also fond of monorhyme; there are instruction books in Chinese telling that more than 100-200 monorhymes might be excessive -- or even compromise the beauty of a poem. Classical persian poetry, which is all tastefully and imaginatively rhymed, sounds heavenly. It is amazing what having just two extra vowels in one's language can do to the sound of poetry. While it is possible, but doubtful, that the Arabs and the Persians discovered rhyme on their own (around the same time as the Irish), it is more likely that rhyme (via Tang poetry) had spread through poetically-inclined merchants along the Silk Road.
The Chinese already had it at 500 BC, perhaps even earlier (Confucius' Book of Songs is the earliest rhymed verse and it is said to be a compillation of poems written as early as 1000 BC). It is remarkable that we still have these rhymed poems because in 213 BC having these poems was a capital offense and all books of poetry had to be burned.
That was a close call for rhyme. Then the nutty emperor obsessed with his own immortality and greatness followed the path of the lesser mortals, and this example led to a greater leniency towards poetry in general and rhyme in particular ever since. By the time of the Tang dynasty, when rhyme started to expand westwards, this episode was ancient history. Rhyme won!
Not so fast ----------
Rhyming in hieroglyphic is an exciting topic of its own, but the very logic of it is that Chinese "rhyme" is presently but a theoretical construct: the exact, phonetical rhyme existed only in archaic and middle languages. The language has changed very considerably in 3000 years, and in today's Mandarin the rhyming is working poorly. What was rhymed poetry just yesterday became something not unlike classical Greek and Roman poetry, with meter but no rhyme. China is where rhyme was invented, but it cannot last there. In Europe, where writing is phonetic, rhyme can last, but only in principle, as the vernacular languages have the life time of a moth. The Arabs and the Persians are in between, and rhyme is rightfully theirs: it became sacred and interlocked with language itself, resisting its change.
It is asserted that rhyming is for the ease of memorization and melodics - or a device for inspiration. All true. But it may serve another role, which is seldom appreciated: holding back. A poem wants to be read in its original language. But this language is water passing through its texture and eroding everything. The pronounciation changes, the words fell out of use, the meanings of the idioms are lost, then the language itself is gone or changed beyond any semblance. It is a battle with time, in which time can only win. The rhyme is a device making this battle to last a bit longer. The poem fights the very language in which it is written, subordinating the life of this language to its own life and rejecting homage to fate. No wonder that the lovers of classical poetry looked at rhyme disapprovingly. Such folly was barbarian through and through.
Why do we rhyme?