I think that it is significant that Beckett included four major characters in Godot. Four has long been a number of completion, stability and predictability, as well as the representation of all earthly things.

In number symbolism, the logic of the number four follows from that of the previous three. One represents the male principle, the "yang". It is raw energy, positive, original and creative. In the creative process it is the original spark of an idea. Two is the feminine principle, the "yin". It is the gestational period in which things begin to form, the earth into which the seed of one’s idea is planted. In the creative process there is almost always a similar period when an original impulse "cooks" for a time, even if only in sleep or distraction. Three is the synthesis of one and two. It is ideation and self-expression, the creation itself, the finished idea. Four is the material manifestation of three, the actual physical realisation, order and systematisation of the idea. It is the making real of the dream represented by three.

Four has come to be considered the number of labour and stability. In the maxim that art is "25% inspiration and 75% perspiration", four is the effort required to put the idea down on paper, to learn the piece and perfect it in rehearsal, to order the media and create the work of art. It is also the number of living the creation as the process. The first stable element in the periodic table is helium, with its four component particles. The first element in the table with four valence electrons is carbon, the basis of all organic life. Negatively it can mean stagnation, fossilization, paralysis, rigidity, or stubbornness.

Even the inclusion of the fifth character, the Boy, has its place in the pantheon of number symbolism, as five is the number of expansion, of destabilisation, of the catalyst. Five becomes the hand that turns the Wheel of Fortune on which the four elements sit, and is the hub around which it spins. Likewise, the visitation from Godot’s representative provides a gravitational centre that forces the four main characters to return to the spot where their collective drama takes place.

One significant representation of four symbology is in the representation of the four evangelists of the four winged beasts in the vision of Ezekiel, later reconstitutes in the New Testament as the four beasts of the apocalypse in the Book of Revelations. In the Kabbalah, there were four worlds of the Tree of Life. There are four creatures on the arms of Freemasonry, four primary mental functions according to Carl Jung, and four dimensions of modern science: length, breadth, width, and time.

The beast with the human face (sometimes considered an angel) represents Matthew, the lion Mark, the eagle John and the ox Luke.

A further expansion of four symbology is represented in the tarot card The Wheel of Fortune. Its connection with Beckett is not really all that whimsical. Beckett had great interest not only in pagan symbology (especially as represented by the figure of Fortune) but also in Jung’s psychology of symbolism. Jung had great interest in what are currently considered "frivolous" occult subjects: astrology, numerology, the Tarot, etc, as sources of cultural and psychological symbology.

In the card are included symbolism of the four Evangelists, the four seasons and the four elements (represented by the symbols for the four fixed signs of the zodiac), the Hebrew letters in the name of God (Yahweh: YHVH), and the four grail symbols (the letters T, A, R, and O).