A leaf is green in summer and brown in autumn. How does four-dimensionalism dissolve the apparent contradiction of one object having incompatible properties?
ABy denying that the summer leaf and autumn leaf are really the same object — they are numerically distinct things
BBy arguing that 'green' and 'brown' are not genuine properties but just linguistic descriptions that change with perspective
CBy distinguishing temporal parts: the green-property is had by the summer-stage and the brown-property by the autumn-stage — different parts of the same 4D object, just as different spatial parts can have different properties
DBy accepting the contradiction and arguing that identity through time is logically impossible
Four-dimensionalism dissolves the problem by analogy with spatial parts. The left half of a road can be smooth and the right half bumpy — no contradiction, because different parts have different properties. Similarly, the leaf's summer temporal part is green and its autumn temporal part is brown. Different parts of the same four-dimensional object have different properties; there is no single entity that is both green and brown at once. The rival endurantist view says the whole leaf is wholly present at both times and must have both properties — which is where the contradiction pressure arises.
Question 2 Multiple Choice
According to four-dimensionalism, what makes you at age 10 and you at age 30 'the same person'?
AYou are numerically identical at both times — the same simple persisting substance
BYou at age 10 and you at age 30 are temporal parts of a single four-dimensional person-worm, connected by overlapping chains of psychological and physical continuity
CThere is no genuine fact of the matter — personal identity through time is a useful fiction
DThe soul provides the underlying identity that physical and psychological change cannot supply
For the four-dimensionalist, 'you at age 10' and 'you at age 30' are distinct temporal stages (not identical to each other) that are both parts of a single extended four-dimensional entity — the spacetime worm that is you. Personal identity is a matter of part-whole relationships and continuity chains connecting the stages, not a separate metaphysical fact of numerical identity between them. This dissolves the puzzle of personal identity through change by relocating it: instead of 'how can the same thing change?', the question becomes 'what connects the stages into one worm?' — answered by physical and psychological continuity.
Question 3 True / False
Four-dimensionalism fits naturally with the B-theory of time because both treat all temporal moments as equally real, making time analogous to space.
TTrue
FFalse
Answer: True
The B-theory holds that past, present, and future are equally real — there is no metaphysically privileged 'now,' just the block universe of all events ordered by earlier/later. This makes time genuinely like a spatial dimension: the whole spacetime manifold exists. Four-dimensionalism maps perfectly onto this picture: objects are extended through time just as through space, with temporal parts at each moment just as spatial parts at each location. The A-theory — where only the present is real and time flows — sits awkwardly with temporal parts (there's nothing to be a 'part of' if past stages no longer exist).
Question 4 True / False
On four-dimensionalism, objects do not truly persist through time — what we call 'the same object' at different times are really just qualitatively similar but numerically distinct things.
TTrue
FFalse
Answer: False
This confuses four-dimensionalism with eliminativism about identity. Four-dimensionalism does claim that objects persist through time — but persistence means 'having temporal parts at different times' rather than 'being wholly present at each time' (the endurantist view). The summer leaf and the autumn leaf are temporal parts of one and the same four-dimensional leaf, not two distinct objects. The four-dimensionalist preserves genuine identity through time; they simply analyze what identity-through-time consists in differently from the three-dimensionalist.
Question 5 Short Answer
How does the analogy between temporal parts and spatial parts allow four-dimensionalism to dissolve the problem of change, and what does this reveal about the structure of the solution?
Think about your answer, then reveal below.
Model answer: The spatial parts analogy shows that having different properties at different locations generates no contradiction — the left and right halves of a road have different surface properties, yet the road is one object. Four-dimensionalism extends this: different temporal parts of an object have different properties at different times, yet the object is one four-dimensional whole. This dissolves the problem by reframing 'how can one thing have contradictory properties?' as 'how can different parts of one thing have different properties?' — which has an obvious, unparadoxical answer.
The structure of the solution is deflationary rather than explanatory: rather than explaining HOW an object retains identity despite change, four-dimensionalism dissolves the puzzle by denying that any single entity has both the old and new property. The main cost is ontological: we must accept temporal parts as genuine entities, and this seems to multiply the things that exist (for every object, also all its temporal stages). Critics find this extravagant; the three-dimensionalist insists the whole object is wholly present at each time and that the puzzle of change must be addressed directly rather than dissolved by gerrymandering the ontology.