With his celebrated and oft-recited Sonnet 116, William Shakespeare offers not so much a definition as a characterisation of what true love is: unshakeable and unaffected by external changes or temptations, steady and dependable as a lodestar in the darkest, stormiest hour, and everlasting "even to the edge of doom."

With its religious overtones that echo the Christian marriage vows and invoke absolute certainties in a world that is inherently uncertain, it speaks to generations of lovers in a language that is direct and easy to understand.

It is hardly surprising, then, that together with Sonnet 18, Shall I Compare Thee to a Summer's Day, and perhaps the nearly as famous Sonnet 29, When in Disgrace With Fortune and Men's Eyes, Sonnet 116 occupies the top spot of Shakespeare's Sonnets 'Greatest Hits', and it is also one of the most confident statements made by Shakespeare about, as much as in, his craft, poetry.

With Sonnet 115 William Shakespeare turns his attention to the perplexing paradox that a love that is experienced as complete and absolute and therefore perfect, such as his love for his young man, may turn out, over time, to have been but a fledgling infant compared to the even fuller, more profound, more mature love that it has the potential to grow into.

In acknowledging that love can evolve and grow over time it sets the premise that love itself is changeable – here for the better, to be more deeply and more sincerely felt than ever before – and it therefore not only concedes, but claims as a lover's right, the necessity, perhaps, to revise statements made about love in the past, and in doing so to effectively give those pronouncements the lie.

With his curiously cryptic Sonnet 114, William Shakespeare poses a rhetorical question to his younger lover, asking whether his experience of seeing him in everything he looks at is down simply to his eye flattering him, or to his eye having acquired the ancient mystical art of alchemy and actually turning even ugly creatures into beautiful angelic beings just such as the young man himself.

He then also settles the matter emphatically and declares without reservation that it is indeed flattery on the eye's part that has this effect on him, but that any sin the mind may be committing in lapping it all up is mitigated by the fact that the eye too loves what it wants to see – the young man's beauty – and so willingly tastes of this flattering, though therefore potentially poisonous, potion first, before passing it on for the mind to metaphorically imbibe.