Point, line and surface as 'nothing'; a weighted wheel
Boundaries that are no part of their body, with an arithmetic of 'nothings'
Leonardo continues his campaign to prove that point, line and surface are 'nothing': the point bounds the line, the line the surface, the surface the body, yet each boundary is no part of what it bounds but only the beginning of the next. Because all things that occupy nothing are equal, he reaches the paradox that many points equal one, the centre of a circle, and that the part equals the whole 'as is proved in arithmetic.' A mechanical figure at the upper right sets a weight a of one thousand against a wheel m weighing two thousand and asks which cord sustains more. Diagrams show squares with diagonals, circles and a wheel hung with weighted cords.
On this page
Point, line, surface and their boundaries
The point is the boundary of the line and nothing can be smaller; the line bounds the surface, the surface bounds the body. Since a boundary becomes the beginning of the next thing and is part of neither, all boundaries occupy nothing, and the body is clothed in surfaces, ringed by lines, and terminated by points.
Many points equal to one at the circle's centre
If infinite lines converge on one point of a circle, each pair enclosing an angle that ends in a point, the many angular points returned into the circle equal the single centre. Thus many points equal one and one equals many, which can only happen 'in nothing'; therefore the point is nothing because it occupies nothing.
Weight a against wheel m, and which cord bears more
A figure sets a weight a exerting one thousand against a wheel m weighing two thousand, asking which cord sustains more, and by how much. A pulley or wheel is drawn with weighted cords hanging from it.
Thickness diminishing as extension grows
All things that can be extended have thickness which diminishes in the same proportion as it grows in extension. Leonardo adds that all 'nothings' are equal to all and all to one, 'as is proved in arithmetic,' and that all motions are caused by abundance or scarcity, being greater where the excess is greater.
