Phil, It’s my feeling that ‘should’ does not generally carry the force of ‘must’ (however, it may with the help of surrounding words – see below). For example, if one said that the speed limit (which in practice really isn’t a limit) of 75 mph on Colorado interstate highways ‘should’ be obeyed. This strikes me as more of a suggestion that one ‘ought to,’ rather than a command to do so. However, in checking through a few dictionaries I found that the definition appears to be somewhat muddled:
Random House Unabridged seems to be saying that it means both MUST and OUGHT: “must; ought (used to indicate duty, propriety, or expediency): ‘You should not do that.’”
Merriam-Webster’s Unabridged never specifically says ‘must’ in any of its 6 definitions, but it does use the word ‘necessity,’ which, as far as I’m concerned, means an ‘imperative’ requirement and thus would seem to have the same force as ‘must.’ However, the only one-word synonym that they offer in their lengthy discussion is ‘ought.’:
2) Used in auxiliary function to express duty, obligation, NECESSITY, propriety, or expediency <“for 'tis commanded I should do so”— Shakespeare> <”but now he is dead, why should I fast”>— 2 Samuel 12:23 (Revised Standard Version)> <“the law was then passed . . . that every senator should take an oath”— J.A.Froude> <“in such cases the officer should first give notice to those in the house”—Paul Wilson> <“and this is as it should be”— H.L.Savage> <”was determined that his son should have a good education”> <“you should brush your teeth after each meal”>
The ‘Shakespeare’ and the ‘senator’ quotes by force of the surrounding words appear to me to be imperatives.
5) Used in auxiliary function to express what is probable or expected <“this year's treasury deficit should be $6 billion or more”— T.R.Ybarra> <effects of the trends cited above should not be felt . . . for another decade”— A.W.Griswold> <it should be child's play for the three of us”—John Buchan> <recordings which should confuse even the most ingenuous listener”— Robert Evett> <“with an early start, they should be here by noon”>
The OED discusses ‘should’ under ‘shall’ and tells us that the imperative ‘shall’ is obsolete: “This conditional form of expression was from an early period substituted for the unconditional ‘shall’ in sense 2, and in modern English the present tense in this use is obsolete, and SHOULD = OUGHT TO.”
The American Heritage Dictionary lists the imperative (under ‘shall’) as archaic: “2) Archaic. a) To be able to. b) to have to; must”
So my vote is that ‘should’ is not an imperative, unless some surrounding words force it into being so. And I would certainly be very wary about using ‘should’ for ‘must’ in any legal document.
Ken – November 9, 2004
Reply from Ken Greenwald (Fort Collins, CO - U.S.A.)