Immateriality of the Soul - Hume

• Book 1, Part 4, Section 5
  •  Of the Immateriality of the Soul
    • "As every idea is derived from a precedent impression, had we any idea of the substance of our minds, we must also have an impression of it."
      • impressions represent substances by resembling the substance
      • the mind is not a substance (according to Cartesians)
      • so, we cannot have an impression of the mind itself
      • if we cannot have an impression of the mind, then how do we get an idea of the mind?
    • Concerning the Cartesian definition of substance as that which can exist by itself
    • everything fits this definition
    • Principle 1: "Whatever is clearly conceived may exist, and whatever is clearly conceived after any manner may exist after the same manner."
    • Principle 2: "Everything which is different is distinguishable, and everything which is distinguishable is separable by the imagination."
    • Perceptions are different from themselves and everything else
    • Perceptions are distinct and separable
    • Perceptions can be considered separately
    • Perceptions can exist separately
    • Therefore, according to the Cartesian definition of substance, perceptions are substances
  • On substance
    • "We have no perfect idea of anything but of a perception."
    • "A substance is entirely different from a perception."
    • "We have, therefore, no idea of a substance."
  • On inhesion
    • "Inhesion in something is supposed to be requisite to support the existence of our perceptions."
    • "Nothing appears requisite to support the existence of a perception."
    • "We have, therefore, no idea of inhesion."
  • Thought and extension are incompatible and cannot incorporate in the same subject
  • Maxim: "An object may exist and yet be nowhere."
    • when its parts are situated so they have no figure or quantity
    • "nor the whole with respect to other bodies"
    • from our perspective, we cannot form any notion of its contiguity or distance
    • true of perceptions and objects other than those of sight and touch
    • they are incompatible with space

Hume, David. Treatise of Human Nature