Taking Ideas Seriously is the skill/habit of noticing when a new idea should have major ramifications.
It has to do with decompartmentalization. By default some people think about one set of ideas in one compartmentalized domain (say, professional scientists thinking about the scientific method), and don’t think to apply those ideas to other domains (such as their religion or politics). People with decompartmentalized beliefs update faster.
Taking a new idea seriously has the advantage of letting you act on it sooner. It can potentially have the disadvantage of making you vulnerable to convincing-but-wrong arguments, if you don’t have the skills to evaluate them properly.