"O ye who believe! When you acquire a loan for a fixed period, record it in writing, and let a scribe write it down between you with fairness; the scribe should not refuse to write, and just as Allah has taught him to write, he should also write for others; the one who has incurred the debt should have [the document] written and fearing Allah his Lord, he should not make any reduction in it. If the debtor is indiscreet or feeble or unable to have it written, let his guardian do so with justice. And call in two male witnesses from among your men, but if two men cannot be found, then one man and two women from among your likable people so that if one of them gets confused, the other reminds her. And witnesses must not refuse when they are summoned. And whether the loan is big or small, be not negligent in documenting the deal up to its period." (2:282)
this verse literally says you should ask 2 men or 1 man and 2 women to be witnesses.
"ask"... meaning the majority of this verse is not talking about court. its talking about the BUSINESS DEAL happening OUTSIDE of court. and is saying to have those sets of witnesses in case it ever DOES go to court so a fair set of witnesses can be provided to the court/judge. the judge can call whomever he or she wants to testify. this way there's a standard the judge can reasonably expect.
the verse really doesn't have much to do with law or court. its social behaviour.
by the way... technically that also means there's 1 female "witness", the second woman just backs up her account. so to say it means 2 women = 1 man even in testimony is kinda off the mark. if you have 2 male witnesses, they could interact again and talk about what they witnessed and remind each other. what if you had 1 man and 1 woman as witnesses? it might even force the woman to interact alone with a strange guy. this would be unusual in an islamic society and very unlikely. if she had a woman backing her up, she's not alone. on top of that, its not out of the question the woman may marry the male witness... in which case she'd have an emotional attachment (and cultural/societal) and could be influenced by her husband's decisions. that's not fair so another witness is needed to break the 1 man/1 woman possible tie. which would be another woman so as not to require the first woman to have to interact again with a non-mahram man too much. so the preference is for 2 male witnesses, since in islamic society they would interact more. and if only one male witness is found, 2 women can substitute for the second. if a male witness 'forgets', his testimony is rejected, the other can't substitute or remind.
it has nothing to do with the worth of one or the other. its based on environmental factors more than anything. "if one of them gets confused, the other reminds her" is attributed to things like PMS more by guys who haven't been around women too often. PMS is not the concern here. That comes around once a month and the odds she'd be called in to testify that day are not great... especially considering if she's exempt from praying/fastying while menstruating, then it stands to reason she can have the court appearance delayed for personal reasons too. the real reason is environmental. in a perfect islamic society, women aren't used to going out of the house for much of anything since they have no responsibilities there and most likely even have servants for the menial daily affairs... let alone being called up to testify in court.
its an experience thing. it wouldn't matter if most women were working outside of the house and could ably participate in court, the law itself has to account for giving the women the right to NOT have to go outside of the house. to give women and men completely equal treatment would give them equal responsibilities which would then rob them of the right which Islam considers they should have... that is to say, they can stay out of the public eye if they so choose. men do not have this priviledge. some women would appreciate that kinda thing.
and again, that is for WITNESSES. i.e, women NOT INVOLVED in the deal. a woman can run a business, in which case, she can't be witness to her own loans now can she? that makes no sense. but if she were called to testify in court as a party involved in the transaction itself, she alone would suffice. not only that, women can be judges. which defeats the entire idea of 'a woman is worth half a man'.
people tend to think that the 1 man/2 women rule applies to circumstantial evidence as well. this is only for business.
and lastly, this verse doesn't indicate a propensity to forget on the part of women. men and women are equally likely to remember or forget something. adam and eve both forgot equally. had either been better people, they would have reminded the other. one person being better than one another comes down to raw heart and soul, always.
Prophet Muhammad(pbuh) said in his last address that nobody is better than anybody else on the account of race or anything else (including gender) except through "piety and good action".