usually contend that the intuitions underlying and guiding the thought experiments are, at least in some cases, reliable. But thought experiments can also fail if they are not properly supported by intuitions or if they go beyond what the intuitions support. In the latter sense, sometimes counter thought experiments are proposed that modify the original scenario in slight ways in order to show that initial intuitions cannot survive this change. Various taxonomies of thought experiments have been suggested. They can be distinguished, for example, by whether they are successful or not, by the discipline that uses them, by their role in a theory, or by whether they accept or modify the actual laws of physics. Critical thinking Critical thinking is a form of thinking that is reasonable, reflective, and focused on determining what to believe or how to act. It holds itself to various standards, like clarity and rationality. In this sense, it involves not just cognitive processes trying to solve the issue at hand but at the same time meta-cognitive processes ensuring that it lives up to its own standards. This includes assessing both that the reasoning itself is sound and that the evidence it rests on is reliable. This means that logic plays an important role in critical thinking. It concerns not just formal logic, but also informal logic, specifically to avoid various informal fallacies due to vague or ambiguous expressions in natural language. No generally accepted standard definition of "critical thinking" exists but there is significant overlap between the proposed definitions in their characterization of critical thinking as careful and goal-directed. According to some versions, only the thinker's own observations and experiments are accepted as evidence in critical thinking. Some restrict it to the formation of judgments but exclude action as its goal. A concrete everyday example of critical thinking, due to John Dewey, involves observing foam bubbles moving in a direction that is contrary to one's initial expectations. The critical thinker tries to come up with various possible explanations of this behavior and then slightly modifies the original situation in order to determine which one is the right explanation. But not all forms of cognitively valuable processes involve critical thinking. Arriving at the correct solution to a problem by blindly following the steps of an algorithm does not qualify as critical thinking. The same is true if the solution is presented to the thinker in a