Which statement most closely defines an assumption in logical reasoning?

An assumption in logical reasoning is understood as a statement or idea that is taken for granted within the context of the argument. For an argument to be valid and to hold true, certain underlying truths must be accepted; these are the assumptions. By choosing the response that defines an assumption as a fact that must be true for the argument to hold, it emphasizes the necessity of these unstated claims in supporting the overall reasoning presented.

In constructing arguments, the explicit premises alone do not always cover the entire logical basis required to arrive at the conclusion. Assumptions fill in the gaps that, if false, could undermine the argument. For instance, if an argument concludes that a new teaching method is effective based solely on limited testimonials, there is an underlying assumption that those testimonials are representative of the broader population, which is critical for the conclusion's accuracy.

In contrast, the other choices refer to aspects of arguments that do not capture the essence of what an assumption embodies in logical reasoning, such as explicitly stated premises or opinions, which do not require the same kind of hidden acceptance essential for assumptions. Therefore, understanding an assumption as something necessary for the argument to hold reveals its crucial role in logical reasoning.