The doctrine of judicial precedent is based on the Latin maxim stare decisis et non quieta mova, which is translated as
to stand by things decided. So in the context of law it conveys the meaning that a previous decision should stand.
Legal principles established in prior decisions set a precedent on specific issues. Inferior courts are bound to follow the decisions of higher courts. This is an essential aspect of the English Common Law system and also impacts on judicial interpretation of legislation.
A case must be decided in the same way as a prior case if the material facts are sufficiently similar. A proposition stated in one case is binding in a later case if it is a proposition of law, part of the ratio decidendi and decided in a court whose decisions are binding on the present court.
Certainty and Consistency
The use of precedent can be seen as a pragmatic measure, once a point of law has been argued and decided upon, there is no need to reassess in each instance.
It can be seen to help produce certainty and consistency. There is a subtle difference between these concepts, it is possible to have consistency without certainty but certainty requires consistency. Certainty implies predicting an outcome, which is difficult to determine in cases as it relies on which facts a court finds to be proved by the evidence. Certainty is further impeded by the discretion given to judges at different stages, such as sentencing powers. So absolute certainty is difficult to obtain. However, precedent helps to establish consistency so it provides a clear starting point for looking at the chances of success in a case.
The consistency and certainty of precedent can result in issues, especially if the original decision is considered wrong or if attitude have developed since the decision. Of course, ultimately Parliament has the option to legislate in order to overcome any such problems but this is a time consuming and costly remedy.
Proposition of Law
A binding proposition must be one of law, not fact. If a point can be proved or inferred from the evidence then it is likely to be a matter of fact not a point of law.
It is not always straightforward to distinguish fact from a point of law, this is especially true in some negligence cases.
Qualcast Ltd v Haynes 
Claimant was an experienced moulder who was injured when he splashed molten metal on his foot. Defendant, his employer, had provided protective footwear but did not ensure workers wore it.
At first instance the judge decided he was bound by a previous decision to find that the defendant was negligent.
House of Lords decided that whether an employer who did not ensure that workers used protective clothing was negligent was a question of fact in each case, and not a proposition of law. In this case it was held that the employer was not negligent as the risk was obvious, injury was unlikely to be serious and the claimant was very experienced.