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  "body": "\n## Statement\n\nPeano defined the notion of \"function\" in a manner somewhat similar to Frege, but without the precision. First Peano defines the sign \"K means *class*, or aggregate of objects\", the objects of which satisfy three simple equality-conditions, *a* = *a*, (*a* = *b*) = (*b* = *a*), IF ((*a* = *b*) AND (*b* = *c*)) THEN (*a* = *c*). He then introduces φ, \"a sign or an aggregate of signs such that if *x* is an object of the class *s*, the expression φ*x* denotes a new object\". Peano adds two conditions on these new objects: First, that the three equality-conditions hold for the objects φ*x*; secondly, that \"if *x* and *y* are objects of class *s* and if *x* = *y*, we assume it is possible to deduce φ*x* = φ*y*\". Given all these conditions are met, φ is a \"function presign\". Likewise he identifies a \"function postsign\". For example if *φ* is the function presign *a*+, then φ*x* yields *a*+*x*, or if φ is the function postsign +*a* then *x*φ yields *x*+*a*.\n",
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