人类总是在已认识的基础上不断向未知前进,在这个认知过程中人类往往采用类比方法. 在平面上,两条直线不能围成一个有限的图形,而三条直线却有可能围成一个三角形.在三维空间,三个平面不能围成一个有限的图形,而四个平面却有可能围成一个四面体.因此,三角形可以与四面体类比,特殊的三角形可以与特殊的四面体类比(见图1和图2). Human beings always advance to the unknown on the basis of recognition. In this cognitive process, humans often use analogy. In the plane, two straight lines cannot form a limited figure, but three straight lines may form a single one. Triangles. In three-dimensional space, three planes cannot confine a finite graph, but four planes may enclose a tetrahedron. Therefore, a triangle can be analogous to a tetrahedron, and a particular triangle can be analogous to a particular tetrahedron ( See Figure 1 and Figure 2).