Notes on Self, Identity, and Metaphysics (Cartesian vs. Kripke Perspectives)
Overview and key ideas
Distinction between physical/concrete things and nonphysical things
Concrete, physical things can exist on their own in reality (e.g., a phone, a table).
Nonphysical things (e.g., a soul/self) may exist, but not in a way that you can touch or observe directly; they’re not things you can place on a table or hand to someone.
The speaker emphasizes that nonphysical things that exist on their own (independent realities) are controversial and tricky.
Core question: What is the self? Is it a physical/biological thing or a nonphysical essence (soul) that persists independently?
The Cartesian view: a nonphysical self (soul) that can persist independently of the body; the core of “who I am” is not reducible to biology.
The Kripke view (as discussed): identity is tied to the body/biology; the self is a biological organism, not an immaterial essence.
Intuition about the self through examples and thought experiments
People have a core of identity that seems invariant, even as physical attributes change. The question is what, precisely, is invariant?
The Trump example is used to probe what remains constant about a person across changing traits and circumstances (appearance, actions, behavior), and whether that invariant is tied to a soul or to biology.
Key concepts and arguments
Concrete vs. nonphysical entities
Ground-level objects (phone, table) exist on their own; nonphysical things, if they exist, are not observable and cannot be touched or placed on a table.
Nonphysical things are tricky to pin down and may not exist as independent realities in the same way physical objects do.
The self: two competing metaphysical pictures
Cartesian picture (nonphysical, soul-based): the self is an immaterial entity with an identity that persists beyond physical changes. The core of who you are would be unchanging and independent of your biology.
Kripke picture (biological/physical): the self is identical to a biological organism; identity is tied to biology and cannot be separated from the body. The core of who you are is linked to your biological history.
The Trump thought experiment (intuitive test of core identity)
If we strip away all attributes (appearance, behavior, etc.), what remains in Donald Trump? If it’s a nonphysical soul, the core should persist despite physical changes; if it’s biology, the core is tied to the living organism.
Arguments in the classroom targeted whether Trump’s core identity could survive changes to parents, biology, or even species, depending on which picture you endorse.
The Cartesian intuition and its limits
Intuition: there could be a “core” that remains the same even if the body changes (e.g., different parents, different biology).
The counterpoint: many intuitions suggest the core identity is bound to the biology (Kripke view), because changing the sperm/ovum/cell lineage would yield a different person.
The Kripke/biology-centered view in detail
If we take Trump’s identity to be rooted in being human (an immutable biological fact) a) being human is a constant feature, b) changes like becoming a tiger would violate the identity because biology changes in a way that would yield a different organism.
The example of altering parents and zygote: Trump’s identity is tied to a specific zygote formed from a specific sperm and ovum; change either parent, and you get a different individual.
The zygote concept: track identity biologically via ancestry, using a simple prime-number tagging system to track which sperm and ovum produced a given zygote and then which zygote became the person.
The prime-number tagging method (a concrete illustration)
Prime numbers used to label gametes (male): 2, 5, 7, 13, 19 (example sequence given).
Non-prime numbers are avoided to prevent easy factorization and to illustrate a clean “tracking” scheme.
Concept: assign a unique prime to each male gamete and a (potentially separate) prime to each female gamete; a zygote is identified by the product of the two primes, e.g., z = 5 × 7 = 35 for a specific sperm and ovum.
This method allows retracing which term (sperm/egg) contributed to a given zygote, modeling a concrete way to link biology to identity in the thought experiment.
The materialist/physicalist implication from the Kripke perspective
When life ends, the body decomposes; nothing nonphysical remains in a way that morbidly persists if you adopt the Kripke view.
The Cartesian self, if it existed, would survive death; the Kripke self would not; this leads to different practical and ethical implications.
Sequences of intuition and discussion about identity over time
Intuition can shift during discussion: some students agree with the Cartesian view (soul persists, unchanging core), others with the Kripke view (biology defines identity).
The teacher emphasizes testing intuitions against a method: philosophical conclusions should be supported by a replicable method or argument, not mere personal belief.
Two competing pictures summarized
Cartesian picture (soul-based self)
Core self is nonphysical, nonmaterial, and independent of the body.
The core should be unchanging even if biology changes (e.g., different parents, different organisms).
If true, there is a persistent nonphysical entity that endures through life, death, and potential reincarnation scenarios.
Practical implications: beliefs about the self could influence long-term care for the environment, moral purpose, and continuity beyond death.
Kripke picture (biology-based self)
Self is a biological organism; identity is tied to biology, ancestry, and the zygote that began the organism’s life.
The core of “who you are” is the biology; changing parents or even the sperm/ovum would yield a different person.
If true, after death there is no nonphysical core that persists; what remains is memory, records, and legacy, not a continued self.
Practical implications: beliefs about the self influence motivation, ethics, and priorities (short-term vs. long-term, environmental stewardship, etc.).
Intellectual and methodological themes
The problem of proof and method in philosophy
Beliefs should be testable or derivable through a methodical process with data that others can verify.
Personal testimony alone is not enough; arguments must be shareable and reproducible, with a clear method and evidence.
The role of intuition in philosophical debate
Intuitions about identity (e.g., whether you could have had different parents and still be you) are used as starting points but must be checked against theories and evidence.
Different people can have valid but competing intuitions; ultimately, the philosophical theory should be evaluated by its coherence, explanatory power, and alignment with evidence.
Practical reasoning and belief about the self
Beliefs about the true self shape practical decisions (e.g., directions to take after class, how to treat the environment, long-term moral commitments).
If the true self is strictly biological, the motivation to care for others and the environment might be framed in terms of survival, reproduction, and species continuity.
If the self includes a nonphysical core, some argue it could encourage long-term ethical commitments beyond personal lifespan; others argue it could undermine motivation depending on what counts as “afterlife” or enduring essence.
The aim of belief and the value of truth
The speaker emphasizes that beliefs should aim for truth and be justifiable by evidence and method; beliefs that cannot be proven or replicated have limited value.
The environment and practical ethics example: different conceptions of the self (Cartesian vs. Kripke) lead to different attitudes toward environmental protection, stewardship, and intergenerational responsibility.
Environmental ethics and motivation across conceptions
Pro-environment motivation can come from either view, but the line of reasoning differs:
Biology-centered view: care for environment is motivated by survival and the well-being of the species and future generations because health of the environment directly affects lives.
Soul/nonphysical-centered view: care for environment can be grounded in long-term, possibly non-temporal concerns; or conversely, the motivation could be weaker if one believes the self is nonphysical and not tied to ongoing bodily survival.
Illustrative examples and details
The zygote and lineage example (biological ancestry)
Fred Trump and Mary Anne McLeod produced many sperm and ova over their lifetimes.
A zygote is formed from a specific sperm and a specific ovum; identity can be traced back to those gametes and their ancestry.
If you change either gamete, you create a different zygote, hence a different organism; this supports the Kripke view that identity is tied to biology.
Observability and empirical claims
Sperm and ova are tangible, observable objects; they are as real as a table (though smaller).
The thought experiment uses tangible biology to ground the discussion about what constitutes the self.
The practical decisions in the classroom discussion
The class engages in a practical exercise: choosing directions and actions after a class ends, showing how beliefs about the self can influence decisions in everyday life.
Example: deciding whether to walk left or right to exit the classroom and where to go afterward; these choices are used to illustrate how beliefs guide practical reasoning.
Final takeaway about metaphysics and identity
There are at least two kinds of things under discussion: a physical/biological self and a nonphysical self (soul).
If the two kinds exist, they could in principle come apart; this separation raises the central philosophical question: which kind is the real self that should be identified with?