The world is full of things that exist . . . ! No disputing that, but is it going to get us anywhere? Things exist either because they have recently come into existence or because they have qualities that made them unlikely to be destroyed in the past. Rocks don't come into existence at a high rate, but once they exist they are hard and durable. If they were not they wouldn't be rocks, they would be sand. Indeed, some of them are, which is why we have beaches! It is the ones that happen to be durable that exist as rocks. Dewdrops, on the other hand, exist, not because they are durable, but because they have only just come into existence and have not yet had time to evaporate. We seem to have two kinds of 'existenceworthiness': the dewdrop kind, which can be summed up as 'likely to come into existence but not very durable'; and the rock kind, which can be summed up as 'not very likely to come into existence but likely to last for a long time once there'. Rocks have durability and dewdrops have 'generatability'. (I've tried to think of a less ugly word but I can't.)
DNA gets the best of both worlds. DNA molecules themselves, as physical entities, are like dewdrops. Under the right conditions they come into existence at a great rate, but no one of them has existed for long, and all will be destroyed within a few months. They are not durable like rocks. But the patterns that they bear in their sequences are as durable as the hardest rocks. They have what it takes to exist for millions of years, and that is why they are still here today. The essential difference from dewdrops is that new dewdrops are not begotten by old dewdrops. Dewdrops doubtless resemble other dewdrops, but they don't specifically resemble their own 'parent' dewdrops. Unlike DNA molecules, they don't form lineages, and therefore can't pass on messages. Dewdrops come into existence by spontaneous generation, DNA messages by replication.
Truisms like 'the world is full of things that have what it takes to be in the world' are trivial, almost silly, until we come to apply them to a special kind of durability, durability in the form of lineages of multiple copies. DNA messages have a different kind of durability from that of rocks, and a different kind of generatability from that of dewdrops. For DNA molecules, 'what it takes to be in the world' comes to have a meaning that is anything but obvious and tautological. 'What it takes to be in the world' turns out to include the ability to build machines like you and me, the most complicated things in the known universe. Let us see how this can be so.
Fundamentally, the reason is that the properties of DNA that we have identified turn out to be the basic ingredients necessary for any process of cumulative selection. If cumulative selection is really to happen in the world, some entities have got to arise whose properties constitute those basic ingredients. Let us look, now, at what those ingredients are. As we do so, we shall keep in mind the fact that these very same ingredients, at least in some rudimentary form, must have arisen spontaneously on the early Earth, otherwise cumulative selection, and therefore life, would never have got started in the first place. We are talking here not specifically about DNA, but about the basic ingredients needed for life to arise anywhere in the universe.
