This study seeks to answer, through an analysis and comparison of the views of Mullā Ṣadrā and Ayatollah Mesbah Yazdi, whether the actions of material beings are merely caused by the laws of nature or whether they are rooted in will and intention. Clearly, knowledge is a necessary condition for any action to be voluntary. Mullā Ṣadrā adopts three different approaches concerning the knowledge possessed by material beings: denial of knowledge, the concomitance of existence and knowledge, and knowledge through an immaterial soul. Ayatollah Mesbah considers material beings to lack any form of presence or knowledge and maintains, based solely on religious and mystical evidence, that material beings possess a celestial (malakūtī) aspect, and are knowledgeable through this aspect. Ayatollah Mesbah Yazdi’s view and apparently some of Mullā Ṣadrā’s statements indicate that the knowledge of material beings is concomitant with agency-by-intention (fāʿiliyyah bi’l-qaṣd). However, it should be noted that the knowledge possessed by material beings is of the kind of presential knowledge and is extremely weak. Therefore, even if it is accepted that the material beings possess knowledge, agency-by-intention cannot readily be attributed to them, unless the influence of immaterial factors (such as the soul) in shaping the behavior of material beings is taken into consideration. Even in this case, however, agency-by-intention genuinely belongs to the immaterial being, while its effects such as the non-uniformity of nature may be inferred from it.