Table of Contents
- Thomas Reid
- Brain-in-a-vat Argument for Skepticism
- First Principles of Contingent Truths
- 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.”
- “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.”
Brain-in-a-vat Argument for Skepticism
First Principles of Contingent Truths
- The existence of everything of which I am conscious.
- That the thoughts of which I am conscious are the thoughts of a being which I call myself, my mind, my person.
- That those things did really happen which I distinctly remember.
- Our own personal identity and continued existence, as far back as we remember anything distinctly.
- That those things do really exist which we distinctly perceive by our senses, and are what we perceive them to be.
- That we have some degree of power over our actions, and the determinations of our will.
- That the natural faculties, by which we distinguish truth from error, are not fallacious.
- That there is life and intelligence in our fellow-men with whom we converse.
- That certain features of the countenance, sounds of the voice, and gestures of the body, indicate certain thoughts and dispositions of mind.
- 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
- Grammatical rules
- Logical axioms
- Mathematical axioms
- Axioms even in matters of taste
- Moral principles
- Metaphysical Principles