Why, we might ask, are Shakespeare's 154 sonnets regarded near universally as the greatest love sonnets in English literature or any literature? And what makes Romeo and Juliet the most famous play about star-crossed lovers? What accounts for the deeply moving expression of love Shakespeare infuses into his works? Accumulated evidence shows that Shakespeare publishes his collected sonnets around twenty years after he starts writing plays to present the nature-based philosophy behind all his plays and longer poems. Shakespeare says blatantly he expects his set of sonnets to be regarded above all others for their expression of love and gives the reasons why. By adhering to the patently visible patterns in the 1609 edition, Shakespeare & Mature Love tracks how Shakespeare develops his understanding of deep and abiding human love in nature. The evidence of the 154 sonnets establishes the enduring grounds on which he bases his emotive comedies, histories and tragedies that move so many to read and perform them thousands of times worldwide on any one day.