Table of Contents

  1. Thomas Reid
  2. Brain-in-a-vat Argument for Skepticism
  3. First Principles of Contingent Truths
  4. First Principles of Necessary Truths

Thomas Reid

  • Hume had argued that there’s no rational foundation for believing there are physical objects.
  • Kant had tried to answer Hume’s skepticism by constructing an elaborate metaphysical system.
  • Thomas Reid, a contemporary of Hume and fellow Scot, tried to answer Hume by appealing to Common Sense.
  • Reid argued that it’s rational to believe the common-sense worldview of physical objects on the grounds that, being part of human nature, human beings can’t believe otherwise.
  • From An Inquiry into the Human Mind on the Principles of Common Sense, 1764, Chapter V: Of Touch, Section VII: Of the existence of a material world:
    • “All reasoning must be from first principles; and for first principles no other reason can be given but this, that, by the constitution of our nature, we are under a necessity of assenting to them.”
      • Principle 5. That those things do really exist which we distinctly perceive by our senses, and are what we perceive them to be.
    • “Methinks, therefore, it were better to make a virtue of necessity; and, since we cannot get rid of the vulgar notion and belief of an external world, to reconcile our reason to it as well as we can; for, if Reason should stomach and fret ever so much at this yoke, she cannot throw it off; if she will not be the servant of Common Sense, she must be her slave.”

Brain-in-a-vat Argument for Skepticism

First Principles of Contingent Truths

  1. The existence of everything of which I am conscious.
  2. That the thoughts of which I am conscious are the thoughts of a being which I call myself, my mind, my person.
  3. That those things did really happen which I distinctly remember.
  4. Our own personal identity and continued existence, as far back as we remember anything distinctly.
  5. That those things do really exist which we distinctly perceive by our senses, and are what we perceive them to be.
  6. That we have some degree of power over our actions, and the determinations of our will.
  7. That the natural faculties, by which we distinguish truth from error, are not fallacious.
  8. That there is life and intelligence in our fellow-men with whom we converse.
  9. That certain features of the countenance, sounds of the voice, and gestures of the body, indicate certain thoughts and dispositions of mind.
  10. That there is a certain regard due to human testimony in matters of fact, and even to human authority in matters of opinion.

First Principles of Necessary Truths

  1. Grammatical rules
  2. Logical axioms
  3. Mathematical axioms
  4. Axioms even in matters of taste
  5. Moral principles
  6. Metaphysical Principles