Does the Opposition role dictate that it must oppose?

Rudd's rescue plan has hit a snag but is unlikely to be stopped by the lone opposition Liberal coalition leader Malcolm Turnbull. While the beauty of democracy is that it provides checks and balances, do the Opposition leaders always have to reject government policies especially when they have no viable or better alternatives? Most would agree that Rudd's stimulus package would be more effective than the tax deductions espoused by Turnbull. Turnbull whose background is in arts, law and logging, wasn't known to hold strong views on economic management. Focussing on the minute details, he has certainly missed out on the bigger picture. Bravery could also constitute folly in some cases.