  A common way of stating the non-cloning theorem -- one of distinguishing
characteristics of quantum theory -- is that one cannot make a copy of an
arbitrary unknown quantum state. Even though this theorem is an important part
of the ongoing discussion of the nature of a quantum state, the role of the
theorem in the logical-algebraic approach to quantum theory has not yet been
systematically studied. According to the standard point of view (which is in
line with the logical tradition), quantum cloning amounts to two classical
rules of inference, namely, monotonicity and idempotency of entailment. One can
conclude then that the whole of quantum theory should be described through a
logic wherein these rules do not hold, which is linear logic. However, in
accordance with a supervaluational semantics (that allows one to retain all the
theorems of classical logic while admitting `truth-value gaps'), quantum
cloning necessitates the permanent loss of the truth values of experimental
quantum propositions which violates the unalterability of the past. The present
paper demonstrates this.
