In day-to-day life, different people observe the same event but report it…

Constructivism in pedagogy holds that learners actively build knowledge rather than receiving it ready-made, but its strands disagree on both WHERE that construction happens (individual experience, social interaction, or a shared culture) and WHETHER the learner is understood to be approximating one real, external world or is instead building an entirely private, self-consistent version of reality with no objective yardstick to check it against.

Here, several people watch the identical event yet describe it differently, and the stem attributes this purely to each person's own worldview — with no group discussion, shared culture, or age/stage difference mentioned. Radical Constructivism (Ernst von Glasersfeld) is the strand that explicitly denies a knower can ever directly verify an objective, ready-made reality; each individual instead builds their own personally viable — but not verifiably 'true' — version of reality purely from experience. Because there is no shared objective anchor to converge on, two people with different personal worldviews are expected to construct, and report, different versions of even the very same event.

This denial of any shared objective anchor is what separates Radical Constructivism from the other strands on offer:

• Social Constructivism — knowledge is built through social interaction and negotiated, shared meaning with others; divergence here would come from different groups jointly constructing different meanings, not from one person's private worldview.

• Cultural Constructivism — understanding is shaped by a community's shared cultural tools, symbols and practices; it explains variation across cultural groups, not variation between individuals who may even share a culture.

• Cognitive Constructivism — a learner's mental schemas mature through developmental stages (assimilation and accommodation) while still adapting toward one actual external world; it does not deny that an objective reality exists or can be approximated, so it does not treat divergent reports as irreducibly private and worldview-driven the way Radical Constructivism does.

Because the variation here is rooted in each person's own subjective worldview rather than group negotiation, shared culture, or developmental stage — and because only Radical Constructivism denies any objective anchor that different knowers could converge on — Radical Constructivism is the correct type.