The parable or other analogy to spiritual truth appropriated from the world of nature or man, is not merely illustration, but also in some sort proof. It is not merely that these analogies assist to make the truth intelligible… Their power lies deeper than this, in the harmony unconsciously felt by all men, and which all deeper minds have delighted to trace, between the natural and the spiritual worlds, so that analogies from the first are felt to be something more than illustrations, happily but yet arbitrarily chosen… They belong to one another, the type and the thing typified, by an inward necessity; they were linked together long before the law of secret affinity.R. C. Trench, Notes on the Parables of our Lord 12-14
This reminds me of my previous curiosity around word-play. How is it that the Old Testament literature works so well? It is as if it were made for this.
And if it was made for the literary connections, is there any other sort of connection between the things used, the signs? Is there an inherent typological value? This is obviously the case with stones. They represent Israel, who represents mankind in a way, and mankind was made from the dust. Rocks are made from the dust as well, and thus they are a natural symbol.
The same works for fire. Fire represents God in the Bible, but Hebrews tells us that God is fire. John tells us that God is light. Light and fire… well, I think you get the connection.
And of course, typology is a sort of proof for Calvinism.