Just like the power of mind, knowledge and other intellectual realities, the soul is “not subject to annihilation.”

Excerpt from a Talk by ‘Abdu’l-Bahá
Residence of Mr. and Mrs. Parsons

Seventh, when a man looks at creation, he sees two things: that which is perceptible to the senses and that which is abstract. The things that are perceptible to the senses, such as vegetables, minerals and animals, that can be seen by the eyes, heard by the ears, smelled, touched or tasted, are subject to change. But rational powers are not perceived by the physical senses. The power of the mind and knowledge are intellectual realities and are not subject to change or alteration. The eye cannot see them; the ear cannot hear them. It is impossible that knowledge, which is an intellectual reality, be changed into ignorance. The soul, too, is one of the intellectual realities: it is unalterable and is not subject to annihilation.