Through a cognitive perspective, semanticists have gained new insights into the essence of metaphors. A number of features of metaphors have been discussed in the past two decades. These features can help us understand the conceptual nature of metaphors. This section purports to expound three main features: systematicity, creation of similarities, and imaginative rationality.

　 Metaphors are systematic precisely because they are conceptual in nature. For example, there are many metaphors which reflect our conceptions of time. Among them, TIME IS MONEY, TIME IS A LIMITED RESOURCE and TIME IS A VALUEABLE COMMODITY are three concepts which are systematically related. These concepts are shown by many English metaphors as listed by Lakoff & Johnson (1980: 7-8):

　　You're wasting my time.
　　This gadget will save you hours.
　　I don't have time to give you.
　　How do you spend your time these days?
　　That flat tire cost me an hour.
　　I have invested a lot of time in her.
　　I don't have enough time to spare for this.
　　You are running out of time.
　　You need to budget your time.
　　Put aside some time for ping pang.
　　Is that worth your while?
　　Do you have much time left?
　　He's living on borrowed time.
　　You don't use your time profitably.
　　I lost a lot of time when I got sick.
　　Thank you for your time.

　 Of these metaphors, some refer specifically to money (spent, invested, budget, profitably, cost), others to limited resources (use, use up, have enough of, run out of), and still others to valuable commodities (have, give, lose, thank you for). The three metaphorical concepts form a conceptual system based on subcategorization and entailment. In modern industrialized societies, time is conceptualized as a valuable commodity, limited resource, and even money, because work and pay are quantified in terms of hours, weeks, and years. TIME IS MONEY entails TIME IS A LIMITED RESOURCE, which entails TIME IS A VALUABLE COMMODITY. The most specific concept TIME IS MONEY is often used to characterize coherently and systematically all those concepts expressed by the metaphors listed.

　 Metaphor can create similarities between the two domains involved. This runs counter to the traditional view which holds that similarities are inherent in the entities themselves. But cognitive linguists hold that the similarities relevant to metaphors are experiential rather than objective. The metaphorical concepts TIME IS MONEY, for example, is not found in all cultures, nor in all historical periods of a particular culture. The correlation between the two semantic categories is established in the process of conceptualization. Out of human experience, the concept of verticality has no relation to health, consciousness, emotion, quality, and virtue. The UP-DOWN orientation is, however, found in many metaphors in which correlations are created. We select a few orientational metaphors below (Lakoff and Johnson 1980: 15-17):

　　HAPPY IS UP; SAD IS DOWN
　　I'm feeling up. My spirits rose. You are in high spirits.
　　I'm feeling down. He is really low these days.

　　CONSCIOUS IS UP; UNCONSCIOUS IS DOWN
　　Wake up. He fell asleep. He dropped off to sleep.
　　He sank into a coma.

　　HEALTH AND LIFE ARE UP; SICKNESS AND DEATH ARE DOWN
　　He's at the peak of his health. He fell ill. He's sinking fast. His health is declining. 　　He dropped dead.

　　GOOD IS UP; BAD IS DOWN
　　Things are looking up. We hit a peak last year, but it has been downhill ever since. Things 　　are at an all-time low. He does high-quality work.

　　VIRTUE IS UP; DEPRIVITY IS DOWN
　　He is high-minded. She has high standards.
　　That was a low trick. That was a low-down thing to do.

　　RATIONAL IS UP; EMOTIONAL IS DOWN
　　The discussion fell to an emotional level, but I raised it back up to the　rational plane.
　　We put our feelings aside and had a high-level intellectual discussion of the matter.
　　He couldn't rise above his emotions.

　 These examples suggest that we use metaphors to create similarities and correlations between two separate categories, so that we can understand one kind of experience in terms of another.

　 Metaphors are characterized by imaginative rationality. They unite reasoning and imagination. Metaphors as a form of reasoning by analogy involve categorization, entailment and inference. By metaphors we understand one kind of thing in terms of another kind of thing. The source domain is always an expression that denotes something physical and concrete, while the target domain refers to something abstract. Through experience in the physical world we form conceptual structure which we then use to organize thought across a range of more abstract domains. The primes of conceptual structures are called image schemas. When we use or understand metaphors, our image schemas are activated. For example, our image schema of CONTAINER is found in many metaphors (Lakoff and Johnson 1980: 30-31):

　　VISION IS CONTAINER
　　The ship is coming into view. I have him in sight. He is out of sight now.
　　There is nothing in sight.

　　STATES ARE CONTAINERS
　　He is in love. We are out of trouble now.
　　He is coming out of the coma.
　　I'm slowly getting into shape.
　　He entered a state of euphoria.
　　He fell into a depression.

　 Some schemas such as the container schema are static; others are dynamic. The path schema is a conceptual structure of movement from a starting point to an end. Our journeys typically have a beginning and an end, a sequence of places on the way. This image schema is also found in many English metaphors such as LIFE IS A JOURNEY and LOVE IS A JOURNEY, which have, interestingly, Chinese equivalents.