The Criterion for the Mental Powers as Being Numerous as Viewed by Ibn Sina, Sheikh Ishraq and Mulla Sadra

One of the fundamental topics in philosophical psychology is the criterion of the multiplicity of the powers of the soul. The main research question is: What has been taken as the criteria for mental powers as being numerous by Ibn Sina, Suhrawardi and Mulla Sadra for multiplicity of souls? How one may view on what they said in the field? Ibn Sina introduces five criteria in terms of differences in intensity and weakness, rapidity and slowness, existence and absence, contradiction and sexual difference as the criteria, and, relying on the rule of alvahid accepts only the fifth criterion. Sheikh Ishraq, limiting the rule of alvahid to the very essence of God, explains the difference and multiplicity of mental powers in terms of different directions and modifications of the soul. Mulla Sadra, having criticized Ibn Sina`s, also examines the distinction of powers based on the criterion of the separation of one power from another and contradiction in the functions of the soul. In this study, while analyzing these criteria critically, we discuss the drawbacks to them, and prove that none of them may be taken as a criterion in the field.