5 ideas
Ruskin treats architecture as a document of the society that produced it: the state of a nation's buildings records its faith, its pride, and how it treated the people who did the work. The decline of Venetian building from Byzantine and Gothic into Renaissance is read as evidence of moral decline rather than as a shift in taste.
Irregular, varied Gothic ornament shows that each carver was allowed to think and invent, and so to make mistakes. Demanding flawless, identical execution turns the worker into a tool, because perfect uniformity can only be had by suppressing the worker's own judgment and imagination.
Ruskin argues that splitting production into tiny repeated tasks does not really divide labour but divides the labourer into fragments of a man. Industrial precision, such as polished glass beads or perfectly regular mouldings, is bought at the cost of workers who are never allowed to use their whole minds.
Gothic builders varied windows, capitals, and ornament within a single building, breaking strict symmetry whenever function or invention suggested it. Ruskin values this variety because it records many individual minds at work, while repetition of a fixed design records only the single mind of whoever issued the orders.
Ruskin drew the capitals, mouldings, and facades he wrote about, measuring and sketching them in detail. Close drawing forces attention to particulars that a casual glance misses, so his arguments rest on what he had observed first-hand rather than on received categories.