Version 1.2 — Conceptual reorganization and clarification of foundational stance.This version refines the conceptual structure of the paper by explicitly clarifying the role of entropy, causality, and irreversibility as primary elements independent of temporal assumptions. The overall logical framework and core results remain unchanged, while the foundational motivation and narrative coherence have been significantly strengthened. This paper proposes a fundamental reorganization of the conceptual foundations of time, spacetime, and causality by treating causality as a primary structure, rather than as a notion defined through spacetime geometry or temporal order. Causality is defined as a constraint structure specifying which transitions are possible and which are forbidden, without presupposing time, temporal evolution, or coarse-graining. By allowing quantum superposition of such causal structures, a quantum causal space is introduced. Irreversible selections within this space define causal histories, and it is shown that, in the continuous limit, these histories necessarily require a one-dimensional extended representation as the minimal and self-consistent structure compatible with quantum superposition. This representation is referred to as a causal superstring. Within this framework, discrete amplitude information cannot be discarded and is instead reinterpreted as continuous contribution densities along causal histories. This leads inevitably to the emergence of a scalar zero mode associated with the projection from causal space to its continuous representation. Requiring quantum (Weyl/conformal) consistency of the causal superstring formulation imposes conditions expressed as the vanishing of beta functions, under which spacetime geometry and gravitational equations arise as consistency requirements, not as prior assumptions. The analysis further demonstrates that, in addition to scalar and tensorial degrees of freedom, a vector-type degree of freedom necessarily remains. This vector degree of freedom is shown to be structurally isomorphic to vector degrees of freedom in conventional quantum superstring theory, without implying physical identification or phenomenological equivalence. This work is foundational and conceptual in nature. It does not propose new dynamical laws, nor does it address phenomenology or empirical verification. Instead, it establishes a logically closed framework in which time, causality, entropy, spacetime, gravity, and particle-like degrees of freedom are repositioned as consequences of a single underlying causal structure. Detailed dynamics, observational implications, and interdisciplinary connections are deferred to subsequent papers. Version 1.1 — Added Appendix B clarifying the scope of the primary discrete structure and its interpretation as quantum causal space. No changes to the main text or core results. This paper proposes a conceptual reorganization of the foundations of time, spacetime, and causality by treating causality as a primary structure, rather than as a notion defined through spacetime or temporal order. Causality is defined as a constraint structure specifying which transitions are possible and which are forbidden. By allowing quantum superposition of such causal structures, a quantum causal space is introduced. Irreversible selections within this space define causal histories, and it is shown that, in the continuous limit, these histories necessarily require a one-dimensional extended representation, referred to as a causal superstring, as the minimal and self-consistent object compatible with quantum superposition. In this framework, discrete amplitude information is reinterpreted as continuous contribution densities, leading inevitably to a scalar zero mode associated with the projection from causal space. Requiring quantum (Weyl/conformal) consistency of the causal superstring representation imposes conditions expressed as vanishing beta functions, under which spacetime geometry and gravitational equations arise as consistency requirements, not as prior assumptions. The analysis further shows that, in addition to scalar and tensorial degrees of freedom, a vector-type degree of freedom necessarily remains. This vector is shown to be structurally isomorphic (type-identical) to vector degrees of freedom in conventional quantum superstring theory, without implying physical identification. This work is foundational and conceptual in nature. It does not claim physical identification with spacetime, gravity, or elementary particles, nor does it address phenomenology or empirical verification. Such questions are explicitly deferred to subsequent work.
Hitoshi Nakamura (Sat,) studied this question.