The number "four" in the Bible represents things being linked together or joined. This is partly because four is two times two, and two represents the ultimate linking between our desire to be good and our understanding of truth. We can also see this in the fact that most buildings are rectangular, with the four sides linking together to make a whole. We also divide directions into four -- north, east, south and west -- and talk about the "four corners" of something meaning all of it. So our special thinking naturally looks at four sides as linking together into a whole.

(Референце: Apocalypse Explained 417; Arcana Coelestia 1686, 9103, 9601, 9767, 9864)

9767. 'Its pillars four, and the bases of these, four' means the forms of good, and the truths springing from them, which support the linking together. This is clear from the meaning of 'pillars' and 'bases' as the forms of good, and the truths springing from them, which provide support, as above in 9761; and from the meaning of 'four' as a linking or joining together, dealt with in 8877, 9601, 9674.