The ontology of theoretical mysticism and its key elements - such as al-a’yān al-thābita (immutable essences) also referred to as God's pre-creational knowledge - can address fundamental issues like determinism and free will and offer a profound insight into the reality of human free will. However, some scholars have regarded belief in al-a’yān al-thābita as implying determinism for both God and humans, necessitating thorough investigation and reflection. This inquiry first requires an explanation of the position of al-aʿyān al-thābita within mystical ontology and subsequently an elucidation of the essence of free will. Ultimately, it must explore whether al-aʿyān al-thābita contradicts the existence of free will in God and humans or serves as a foundation for its articulation and affirmation. This paper, employing a descriptive-analytical method and drawing on library resources, aims to delve into this issue. It seeks to present, first, an accurate interpretation of the position of aʿyān thābita, followed by a novel understanding of the reality of free will, which is often overlooked. Finally, this paper demonstrates the lack of correlation between belief in al-aʿyān al-thābita and the notion of God or humans being compelled.