What on earth does 5th-Century-BC Greek Philosophy have to do with IT’s Strangler pattern

An excerpt from the book - A Seat at the Table: IT Leadership in the Age of Agility By Mark Schwartz

Theseus, a great hero, is given a ship as a present from the Greeks. After a few years, Theseus finds that one of the ship's wooden planks is becoming a little worn, so he has it replaced. At this point, we ask, does Theseus still have the same ship, or is it now a different ship? Most of us would say that it is the same ship. Can we agree that replacing one plank in a ship doesn't make it a whole different ship? Good.

Over the next few years, one plank after another starts to wear out, and each time Theseus has it replaced. Finally, one day, Theseus realizes that he has now replaced every plank in the ship—there is not a single material thing in the ship that was there when he was first given it. And he wonders … is this still the same ship? Or does he now have a different ship? And if so, when did it become a different ship? If it is the same ship, then what makes it the same?

It could never have become a different ship. Each time Theseus replaced a plank, it was still the same ship it was before he replaced the plank—remember that we said that changing a single plank does not make the boat a different boat. Therefore, the boat could never have become a new boat. But how is it the same boat if it has nothing in common with the original boat?

In the eighteenth century, Thomas Hobbes added another twist to the paradox. As Theseus throws out each worn plank, his neighbor gathers it up. The neighbor reassembles the discarded planks into a boat, putting each plank right where it had been in Theseus's original boat. In the end, he has a complete boat that is “identical” to Theseus's original boat. Now, which boat is Theseus's original boat—Theseus's or the neighbor's?

That's the thing—when you study philosophy, you often feel like the ancient Greeks had already figured everything out. Now it turns out that they already understood IT.

Theseus's activities fall into what the software world now calls the strangler pattern: a way to incrementally modernize a legacy system as defined by Martin Fowler. Instead of building an entirely new system, we take a small piece of the legacy system and rebuild it in a way that lets it interoperate with the rest of the legacy system. We launch that piece into production and have users use it seamlessly as if it is part of the legacy system. Then we take another piece out of the legacy system and do the same thing. And another. And another. Until eventually there is nothing left of the legacy system—it has vanished, piece by piece, like Alice in Wonderland's Cheshire Cat. Or has it? To use Fowler's term, we have strangled the poor cat—I mean the IT system—without ever replacing it; modernized it without ever modernizing it. It is possible to transform without undertaking a transformation project.