an existent either subsists in itself or subsists in something else. Likewise, we know that an existent is either a body or an accident, either occupies space or subsists in something that occupies space; similarly, we speak of it as living, capable, and so forth. In the same way that we know this, we know that an existent either subsists in itself or subsists in something else—provided one understands the meanings of these technical expressions. Whoever understands each of these and conceives it fully thereby acquires self-evident, necessary knowledge rooted in natural disposition. For by self-evident knowledge they mean that merely conceiving the two terms suffices for assenting to the proposition. Failure to assent, therefore, often results from a failure to conceive