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  • 昔者庄周梦为蝴蝶,栩栩然蝴蝶也。自喻适志与!不知周也。俄然觉,则蘧蘧然周也。不知周之梦为蝴蝶与?蝴蝶之梦为周与?周与蝴蝶则必有分矣。此之谓物化。
    - The 'Equivalence of Things' (齐物论) chapter of the Zhuangzi (庄子) (c. 3rd c. B.C.E.)

    Once upon a time I, Zhuang Zhou (庄周), dreamt I was a butterfly.
    Flapping my wings in true butterfly fashion, I was happy as could be, and I knew nothing of any person named Zhuang Zhou.
    But suddenly I awakened, astonished to be Zhuang Zhou.
    I still don't know whether as Zhuang Zhou I was dreaming I was a butterfly or whether as a butterfly I was dreaming I was Zhuang Zhou.
    There ought to be a difference between Zhuang Zhou and a butterfly, but this is called the transformation of things.
    - David K. Jordan translation (adapted)

    Academic Skepticism

    René Descartes
    (17th c. C.E.)

    (2nd c. B.C.E.)

    Skepsis is the Greek word for 'investigation'

    1. Cartesian skepticism is named after René Descartes and his skeptical arguments in Meditations on First Philosophy (1641)
    2. Cartesian skepticism has also been characterized as academic skepticism, in recognition of an ancient (3rd c. B.C.E.) and similar strand of skepticism that arose from the Academy (first founded by Plato)

    1. The academic skeptics were interested in whether there are kataleptic phantasiai (or true impressions)
    2. The academic skeptic's concern about whether there can be such things as true or kataleptic impressions is retained in Descartes

    Recall the following characterization of Cartesian skepticism or academic skepticism:
    1. Cartesian skepticism or academic skepticism:
    2. S1: The only justified attitude with respect to any proposition in a field of propositions F is suspension of judgment
    3. S2: We should believe that S1

    The field of propositions F to which Cartesian and academic skeptics typically extend suspension of judgment may be characterized in terms of external world propositions

    Lu Zhi's (c. 1550) The Butterfly Dream

    Examples of skeptical hypotheses entertained by the Cartesian or academic skeptic:
    1. SH1: I am being deceived by an evil demon
    2. SH2: I am dreaming
    3. SH3: I am hallucinating or suffering from a delusion
    4. SH4: I am insane
    5. SH5: I am a brain in a vat
    6.   ⋮      ⋮

    Argument in favour of Cartesian or academic skepticism:
    1. P1: If I do not know that ∼SH1/SH2/etc, then I do not know that φ1.
    2. P2: I do not know that ∼SH1/SH2/etc.
    3. C: ∴ I do not know that φ1. - valid (modus ponens)

    1. According to the Cartesian skeptic:
    2. I can replace φ1 with other propositions about the external world and still end up with a similar skeptical conclusion