Ling's Notes

Theory of Knowledge

2 min read

Philoshophy

I think therefore I am.

René Descartes discovered certainty by doubting everything until he found something indubitable: the act of thinking itself. Because he was thinking (and doubting), he knew he must exist, famously concluding “Cogito, ergo sum” (“I think, therefore I am”). He rejected sensory evidence, using radical doubt to establish that only the existence of his own mind is certain.

Question: How do we know anything?

How to Know (Descartes’ Method):

  • Method of Radical Doubt: Descartes decided to reject any idea that could be doubted, including the existence of his body, the physical world, and sensory input, which he noted could be deceptive.

  • The Cogito (“I think, therefore I am”): Even if a “demon” is deceiving him, or he is dreaming, he must exist to be deceived or to have those thoughts. The very act of doubting one’s existence confirms it.

  • Rationalism: Knowledge is not gained through senses but by clear and distinct perceptions of the mind (reason).

  • God as Guarantee: Descartes argued that because he has an idea of a perfect God, that perfect being must exist and would not allow him to be fundamentally deceived about reality.

Propositions

      ____________   ___________
     /            \ /            \
    /              X              \
   /              / \              \
  /              /   \              \
 /              /     \              \
/              / KNOW- \              \
\    TRUTHS    \ LEDGE /   BELIEFS    /
 \              \     /              /
  \              \   /              /
   \              \ /              /
    \              X              /
     \____________/ \____________/

  • Left circle: Truths (all true propositions).

  • Right circle: Beliefs (all propositions someone believes).

  • Overlap: Knowledge (propositions that are both true and believed).

Graph View