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A Calculus of Number Based on Spatial Forms - University of ...

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10<br />

Table 2.1: Deniti<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> Spencer-Brown <str<strong>on</strong>g>Number</str<strong>on</strong>g>s.<br />

<str<strong>on</strong>g>Number</str<strong>on</strong>g>s<br />

0 !<br />

1 !<br />

2 !<br />

3 !<br />

Operators<br />

a + b ! ab<br />

ab! a b<br />

a b ! b :a<br />

Rules<br />

at bt :::<br />

:<br />

=<br />

:<br />

= a b ::: t<br />

a = a<br />

:a =<br />

With space as additi<strong>on</strong>, the natural numbers are easily formed. The void acts<br />

as zero and counting proceeds by accumulating marks: , , , ::: and<br />

so <strong>on</strong>. <str<strong>on</strong>g>Number</str<strong>on</strong>g>s are added by spatial collecti<strong>on</strong> whereas multiplicati<strong>on</strong> and power<br />

operati<strong>on</strong>s are composed using marks. Spencer-Brown's numbers are summarized in<br />

Table 2.1.<br />

He gives two axioms for calculating <strong>on</strong> these forms, universe and transfer. With<br />

these axioms he derives many theorems, including reexi<strong>on</strong> and null power. Universe<br />

and null power are his numerical versi<strong>on</strong>s <str<strong>on</strong>g>of</str<strong>on</strong>g> calling and crossing.<br />

Universe<br />

Transfer at bt :::<br />

Reexi<strong>on</strong> a = a<br />

Null Power :a =<br />

:<br />

=<br />

:<br />

= a b ::: t<br />

In additi<strong>on</strong> to the mark, he uses a vaguely dened col<strong>on</strong> to disambiguate c<strong>on</strong>icting<br />

results whichwould equate 0 1 ! : and 2 ! . This col<strong>on</strong> does not completely<br />

resolve the problems it was introduced for.<br />

These numbers add by spatial collecti<strong>on</strong>. For example, 3 + 2 = 5.<br />

3+2 Given<br />

+ <str<strong>on</strong>g>Number</str<strong>on</strong>g> Rewrite<br />

Additi<strong>on</strong> Rewrite<br />

5 <str<strong>on</strong>g>Number</str<strong>on</strong>g> Rewrite<br />

<str<strong>on</strong>g>Number</str<strong>on</strong>g>s multiply by the form ab ! a b . The form reduces by transfer, which<br />

distributes the whole <str<strong>on</strong>g>of</str<strong>on</strong>g> <strong>on</strong>e number throughout the units <str<strong>on</strong>g>of</str<strong>on</strong>g> the other. For example,<br />

3 2=6.

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