Reasons, in law, refer to the explanation which a decision-maker gives for arriving at a particular decision, and define the extent to which that decision maker must justify what they have decided. There are parallels between the decisions of the representatives of a public body (conventionally called the “decision-maker”, usually a civil servant) and of a judge.

Reasons of a judge will be recorded in their judgment, which may be reported. If those reasons refer to questions of law and are critical to the decision, they form the ratio decidendi of the case.

At common law there is technically no duty to provide reasons; but in practice courts – especially appeals courts and courts dealing with judicial review of decisions of public bodies – make frequent reference to the need for judges and decision-makers, from their different stand-points, to provide reasons for their decisions. (The parental: “Because I say so” is not good enough.)

For example in R v Knightsbridge Crown Court, Ex parte International Sporting Club (London) Ltd [1982] QB 304, 314-315,  Griffiths LJ said:

“It is the function of professional judges to give reasons for their decisions and the decisions to which they are a party. This court would look askance at the refusal by a judge to give his reasons for a decision particularly if requested to do so by one of the parties. It does not fall for decision in this case, but it may well be that if such a case should arise this court would find that it had power to order the judge to give his reasons for his decision.”

The books on judicial review apply the same principles to public body decision-makers; and in Padfield v Minister of Agriculture, Fisheries and Food [1968] AC 997, [1968] 2 WLR 924 the House of Lords said that if civil servants failed to give a reason, the court could assume that they did not have one or that they were acting unlawfully.

Reasons are particularly important where the decision-maker has exercised a discretion, to demonstrate that it has not been exercised in a random or arbitrary way.