Locke and Hume both discuss impressions and how they relate to knowledge and ideas. Locke means "returning to commonsense" as rejecting innate ideas and instead believing that all ideas come from experience and sensation. For Locke, impressions are the experiences or sensations we have that form the basis of our ideas. Hume also discusses impressions as the fundamental experiences or sensations that give rise to ideas. For Hume, we cannot know for certain the relationship between cause and effect, but can only observe regular patterns based on past impressions and experiences. Both Locke and Hume see impressions as the foundation for ideas and knowledge, rejecting innate ideas in favor of empiricism.