[FOM] Why inclusive disjunction?

Francis Davey fjmd1 at yahoo.co.uk
Wed Jan 10 04:08:00 EST 2007

John Baldwin wrote:
> I am preparing to teach a course in `proof'.
> Can anyone provide a principled reason for why logicians choose to
>   interpret "or" as inclusive disjunction?
> I understand that in the interpretations of statutes, the exclusive or
> is the default.  So attorney's have made a different choice of 
> `formalization'.

That's not my experience of the law in England and Wales (where I 
practice), but I stand to be corrected (and would be very interested in 
being so).

Consider the following uses of the word "or" in Part 3 of the Civil 
Procedure Rules 
which deals with the court's case management powers.

Note: its our drafting style to use one connective at the end of a list 
as shorthand for the use of the connective between all members of the 
list, eg:

(1) A;
(2) B; and
(3) C

means A and B and C, marked up for readability.

The usual use of "or" is inclusive, for example, under Rule 3.4(2):

"(2) The court may strike out (GL) a statement of case if it appears to 
the court –
(a) that the statement of case discloses no reasonable grounds for 
bringing or defending the claim;
(b) that the statement of case is an abuse of the court’s process or is 
otherwise likely to obstruct the just disposal of the proceedings; or
(c) that there has been a failure to comply with a rule, practice 
direction or court order."

Any, or all of (a) to (c) will trigger the court's power.

Where an inclusive or is not desired the drafter will signal that fact, 
eg under Rule 3.3(5):

"(6) An application under paragraph (5)(a) must be made –
(a) within such period as may be specified by the court; or
(b) if the court does not specify a period, not more than 7 days after 
the date on which the order was served on the party making the application."

which is roughly of the form A or (not A and B).

I am not sure how much this distinction matters in practice since, as 
you know, in English, conjunctions such as "and" and "or" are affected 
by surrounding polarities and other contextual effects.

Francis Davey
1 Middle Temple Lane Chambers
Tel. 020 7353 8988 Mobile. 0781 686 8998 Fax. 020 7353 8269

All New Yahoo! Mail – Tired of Vi at gr@! come-ons? Let our SpamGuard protect you. http://uk.docs.yahoo.com/nowyoucan.html

More information about the FOM mailing list