Shin is one of the 3 Mother Letters: Awareness.
It is the twenty-first letter of the Hebrew Alphabet. Its numerical value is 300.
Shin corresponds to the upper horizontal path of the Tree of Life, the path which connects Hokhma to Bina.
Sepher Yetzirah says about Shin: “…make Shin king over fire, bind a crown to it, and combine one with another. And with them seal heaven in the Universe, the hot in the Year, and the head in the Soul, the male with שאמ and the female with שמא.”
The shape of Shin reminds us three tongues of flame coming from the same log. It is the graphical representation of the desire for Knowledge and Enlightenment. The three tongues of flame are the thinking capability of the human being.
The shape of Shin has a very important characteristic for Kabbalah: it is symmetrical. This symmetry is called Chen (חן), and has been explained as the fundamental requirement for the fulfillment of our Enlightenment.
Symmetry and balance between rational and intuitive thought open the path to the third brain. The well balanced thought lead the human being to the third flame that represents the third eye, the inner eye.
How can we achieve this result?
The answer is hidden in the letter. Shin as Sheket (שקט) meaning relaxation, silence, tranquillity. Shin as Shalom (שלום) meaning peace. Meditation is the mean to access the powerful energies of our brain.
By relaxing, closing our eyes, and letting it go for a few minutes every day, we can start to attain the powers of our wonderful brain.
One last recommendation: beware that Shin is fire. Fire can enlighten our path and warm us up, but it can also burn and destroy. Please avoid to focus your mind on this letter for a long time, otherwise you may be affected by its side effects.