Final answer:
Mutual gains from voluntary trade require differences in opportunity costs as traders can benefit from the comparative advantage. While trade can have negative effects on certain groups, such as job losses, economists generally believe in embracing the gains from trade and addressing issues through other policy measures rather than restricting trade.
Step-by-step explanation:
Mutual gains from voluntary trade require differences in opportunity costs. This is because opportunity costs represent the value of the best alternative foregone when a choice is made. If two trading parties have different opportunity costs for producing goods, they can each benefit from trade by obtaining goods more cheaply through trade than if they produced them on their own. The common belief among economists is that it is better to embrace the gains from trade and then deal with the costs and tradeoffs with other policy tools, rather than cutting off trade to avoid the costs and tradeoffs.
Regarding the question about trade policies and protecting jobs, economists argue that while in practice it is not always possible to compensate those who lose from trade (e.g., workers who lose jobs due to imports), it does not necessarily mean that trade should be inhibited. Instead, it might be more beneficial to have mechanisms in place that can help mitigate the negative effects of trade on certain groups, while still allowing the overall economic benefits of trade to prevail.