General Book of the Tarot, by A. E. Thierens, [1930], at sacred-texts.com
"Occult explanations attached to this card are meagre and mostly disconcerting." (W.) The reason for this is easily seen: the principles of Uranus and Neptune were not much known in antiquity save that they were the general principles of the Heavens (the Air or also the atmosphere) and the Ocean, and as such we find them in the Pantheon and in the original Tarot, not yet as the much later discovered planets, which personify these general cosmic principles. Later ages added very little, if anything at all, to those original explanations. Still Ouranos and Poseidon were known in Greece as well as Dourga and Varouna in India.
And the stone tower struck by a flash of lightning is another version of the legend of Ouranos mutilating his son Chronos, which means, that Heaven is not content with a body of fixed dimensions and form, nor any heavenly force with the limitations put to it
by physical authorities or architects. This may warn man, not to build upon physical existence alone or to think himself safe upon a material basis, however high and solid it may appear from a material point of view. The general meaning, however, is not incidental but essential. ". . . the ruin of the house of life, when evil has prevailed therein" (W.) is one of many possible occurrences; it may signify 'blighted ambitions and hopes,' etc. (P.), but the universal and every day significance is: the renewal of the form, or rather of embodied life, by the force of Heaven, and of microcosm by the life of macrocosm, which incidentally of course breaks up forms here and there, if they are no longer fit for survival; the house of doctrine as well as every structure made by vanity, dogmatism and separativeness.
The Hebrew letter Ayin is addicted to this card. P. utterly fails in giving any elucidation of this relationship. W. has put it very clearly in this quotation: "Except the Lord build the house, they labour in vain that build it."
So the card of the Tower signifies the relation between macro- and micro-cosm and will mean rupture, sudden disillusion, disenchantment, but also it symbolises intuition, renewal, help from above and clear insight in relation to vanity and sham projects, illusion and meaningless formalism.