ΛCDM is an evolution model, not an origin model: it takes a hot, dense, expanding state as its starting point and integrates forward. Traced backward, general relativity predicts an initial singularity where density and curvature diverge (Penrose 1965; Hawking-Penrose 1970), which is not a physical event but the point where the theory stops working; earlier than about 10−43 seconds the model requires a quantum theory of gravity that does not yet exist. Inflation was added to repair the horizon and flatness problems, but the Borde-Guth-Vilenkin theorem (2003) shows that any spacetime with positive average expansion rate is geodesically past-incomplete, so inflation cannot be extended eternally into the past and the question of a beginning returns. What banged, why it banged, and what existed before are questions ΛCDM cannot pose, let alone answer.
The initial conditions are pure inputs. The universe began in an extraordinarily low-entropy state; Penrose estimates the required phase-space precision at one part in 1010123, the most extreme fine-tuning anywhere in physics. Inflation does not explain this, it relocates it: initiating inflation itself requires a rare, smooth, low-entropy patch, and the inflaton field and its potential have no fundamental derivation. The amplitude and spectrum of the primordial perturbations, the baryon content, and the matter-antimatter asymmetry are likewise dialed in at the boundary rather than derived. Because time itself begins at the singularity in the standard picture, causal explanation terminates by construction: there is no earlier state from which the initial conditions could have been inherited.
The standing of the problem is openly contested even among the theorem's authors: Vilenkin reads the BGV result as evidence for an absolute beginning, while Guth maintains the universe is likely past-eternal, and Easson and Lesnefsky have exhibited inflationary solutions that evade the theorem and are geodesically complete. Alternatives such as bouncing cosmologies, conformal cyclic cosmology, the no-boundary proposal, and string-gas or quantum-gravity origins all remain observationally undiscriminated. In operational practice ΛCDM simply begins at the hot dense state and stays silent about its cause, leaving the origin of our patch of spacetime, and whatever preceded it, outside the standard model of cosmology entirely.