Souls and Words: Nefesh HaChaim 2:16

It is known that a person's soul has three levels, known as Nefesh, Ruach, and Neshama, that are connected to three aspects of existence: actions, speech, and thought. These three aspects are the complete human being.

So too each word has three aspects related to deed, speech, and thought, as well as Nefesh, Ruach, and Neshama. They are the letters, the letter, vowels, and cantilation marks. As it is said in the introduction to Tikunim (a mystical work), the cantillation marks are the Neshama, the vowels Ruach, and the letters are Nefesh.

The letters have the aspect of action, for the letters can only come into existence by means of action, such as writing. such as writing a Torah scroll without the vowels. A word cannot come from the mouth without the vowels. Thus letters alone, without vowels, relate to the soul's aspect 'Nefesh,' and with regard to existence, letters relate to the aspect action.

Vowels relate to Ruach, for vowels come with letters by means of words from a person... A person lives by means of the Ruach within him or her, and when the Ruach leaves the person is dead, and when a portion of the person's Ruach is left the person still lives. So too the essence of the life and motion of letters is the vowels, for without them letters cannot come out of the mouth...

The cantillation marks of words are related to the thought and the heart's intention, which are the Neshama. They move the vowels and letters.