However, the relevance of evidence is ordinarily a necessary condition but not a sufficient condition for the admissibility of evidence. For example, relevant evidence may be excluded if it is unfairly prejudicial, confusing, or the relevance or irrelevance of evidence cannot be determined by logical analysis. There is also general agreement that assessment of relevance or irrelevance involves or requires judgements about probabilities or uncertainties. Beyond that, there is little agreement. Many legal scholars and judges agree that ordinary reasoning, or common sense reasoning, plays an important role. There is less agreement about whether or not judgements of relevance or irrelevance are defensible only if the reasoning that supports such judgements is made fully explicit. However, most trial judges would reject any such requirement and would say that some judgements can and must rest partly on unarticulated and unarticulable hunches and intuitions. However, there is general (though implicit) agreement that the relevance of at least some types of expert evidenceparticularly evidence from the hard sciencesrequires particularly rigorous, or in any event more arcane reasoning than is usually needed or expected. There is a general agreement that judgments of relevance are largely within the discretion of the trial courtalthough relevance rulings that lead to the exclusion of evidence are more likely to be reversed on appeal than are relevance rulings that lead to the admission of evidence.