There is a brick-and-concrete fireplace in Le Corbusier's Maison a Weekend at St Cloud (1935) - carefully analysed by Kenneth Frampton in the middle of this interesting study - that is so roughly put together that one initially just thinks 'bad brickwork'.
At the monastery of La Tourette (195760), I've seen people throw up their hands in horror at the beton brut - a grossly uneven surface hacked by the rough nailing of the badly-sawn timber formwork, crudely ripped away, leaving slivers of wood in the concrete.
While the machine aesthetic, in its subsequent developments after Le Corbusier himself had abandoned it, led to ever more abstraction of the intellectual architectural process from the practical building process, the different path that Le Corbusier embarked on after about 1935 took him towards a hand-made, low-tech crudeness that cannot be represented in drawings or on models, and certainly not by any computer.
Beginning at St Cloud, he allowed sloppiness of execution - or rather, a non-control freak attitude to what happens on site - to become the major new factor.
This put humanity into Modern architecture and gave it new links back into tradition - a certain tradition - that allows for the direct expression of the collective thought and work that go into building.
Leaving aside all the other ways there are of thinking about Le Corbusier's development - which was not just a career but the spiritual path of a man who in many ways embodied the culture of his time (including its cruelties) - this shift from the pristine to the rough still marks the point at which architects divide.
Some pursue a form of construction that aspires to absolute precision, while others search for feelings and immediacy by building in a way that allows stains to drip where they will, rough uneven surfaces to catch the light in different ways, and junctions to be violent rather than smooth: the Smithsons, Stirling, Correa or Barragan rather than Chipperfield, Allies and Morrison, or Foster - a rough attitude that cannot be drawn on paper or simulated on a screen.
The paradigmatic shift in the work of Le Corbusier represents a revolution within the continuous revolution of modernity, which enabled architecture to lose its Eurocentricity and Le Corbusier himself to practise in third-world places like Chandigarh. There the intellectual sophistication ofhis sections and plans, and the labyrinthine sequences of his interior spaces, meet the intense sunlight of the Punjab with rough surfaces and deliberately non-pristine junctions and details, made by real men with real feelings.
All architects have to make this decision either to go for reticence, control and repression - in the way of those British contemporaries I mentioned - or to express feelings and strength of character through the processes of building on site (and you can see which side I'm on).
If Le Corbusier had only done one thing in his remarkable life - too easily dismissed by armchair critics who have never tussled with these processes - it would have been his decision to abandon the machine aesthetic.
The masterpieces he then went on to build - the Marseilles Unite, La Tourette, Ronchamp; buildings that have the presence of giant, breathing, sentient beings - will change everything for any architect who dares visit them.
Kenneth Frampton heads the school of architecture at Columbia University, New York, and is one of the most prolific and authoritative voices in architectural writing.
His small volume is an important contribution: of manageable size, divided into short staccato chapters, it points the reader towards deeper investigations and in this sense is an ideal introduction.
It is full of problematic explanations of highly contentious aspects of Le Corbusier's work (most notably, his ideas about cities), drawing the reader into the cultural minefield he left behind. If you like architecture to be challenging and problematic as Le Corbusier's is, then Frampton, I think, has a good touch.
Thomas Muirhead is an architect in London