So, I’m sitting in the little park next to the Borromini church: San Carlo alle Quattro Fontane.
I have eaten my focaccia alla caprese and I’m talking to a cat about Borromini. Unlike one’s family and students, cats might listen, particularly if they think there might be some mozzarella left. And, it’s back to the ‘convincing’ theme.
With Borromini it is the combination of balanced and tweaked proportions. I was thinking back to how the young Raphael didn’t get these sorts of vertical rhythms quite right for the context in his early Deposition. But here, the distance between paired pilasters for example and the slightly larger distance than the standard Vitruvian proportion between them and the next element is famously convincing. It gives exactly the right sort of powerful, muscular sense of movement, carefully prefigured of course in the facade.
But, convincingness in art depends on removing everything that isn’t necessary (‘Everything is purged from this painting but art’, John Baldessari, 1966). Borromini is suitably minimalist in this interior. But notice also his care with details, look at the capitals. Look at the http://www.bluffton.edu/~sullivanm/italy/rome/carlofontane/0069.jpg
band between the volutes, where you might expect to see and egg and dart moulding, in one pair there is a laurel wreath, but the next pair has pomegranates, often a symbol of the resurrection. The wreath theme is continued around the oval of the dome, but not the pomegranates. And that care with proportion and minimal detail is even more noticeable in the crisp details in the windows as you go down to the crypt.
Pigeons are marching along the path where I sit, the cat ignores them, content to think about Borromini.