let S be IncSpace; :: thesis: for A being POINT of S holds

not for B, C, D being POINT of S holds {A,B,C,D} is planar

let A be POINT of S; :: thesis: not for B, C, D being POINT of S holds {A,B,C,D} is planar

set L = the LINE of S;

consider B being POINT of S such that

A1: A <> B and

B on the LINE of S by Lm1;

not for C, D being POINT of S holds {A,B,C,D} is planar by A1, Th47;

hence not for B, C, D being POINT of S holds {A,B,C,D} is planar ; :: thesis: verum

not for B, C, D being POINT of S holds {A,B,C,D} is planar

let A be POINT of S; :: thesis: not for B, C, D being POINT of S holds {A,B,C,D} is planar

set L = the LINE of S;

consider B being POINT of S such that

A1: A <> B and

B on the LINE of S by Lm1;

not for C, D being POINT of S holds {A,B,C,D} is planar by A1, Th47;

hence not for B, C, D being POINT of S holds {A,B,C,D} is planar ; :: thesis: verum