Conceptual Metaphor is at the center of a complex theory of how the brain gives rise to thought and language, and how cognition is embodied. All concepts are physical brain circuits deriving their meaning via neural cascades that terminate in linkage to the body. That is how embodied cognition arises.
Primary metaphors are brain mappings linking disparate brain regions, each tied to the body in a different way. For example, More Is Up (as in "prices rose") links a region coordinating quantity to another coordinating verticality. The neural mappings are directional, linking frame structures in each region. The directionality is determined by First-Spike-Dependent Plasticity. Primary metaphors are learned automatically and unconsciously by the hundreds prior to metaphoric language, just by living in the world and having disparate brain regions activated together when two experiences repeatedly co-occur.
Complex conceptual metaphors arise via neural bindings, both across metaphors and from a given metaphor to a conceptual frame circuit. Metaphorical reasoning arises when source domain inference structures are used for target domain reasoning via neural mappings. Linguistic metaphors occur when words for source domain concepts are used for target domain concepts via neural metaphoric mappings.
Because conceptual metaphors unconsciously structure the brain's conceptual system, much of normal everyday thought is metaphoric, with different conceptual metaphors used to think with on different occasions or by different people.
A central consequence is the huge range of concepts that use metaphor cannot be defined relative to the outside world, but are instead embodied via interactions of the body and brain with the world.
There are consequences in virtually every area of life. Marriage, for example, is understood in many ways, as a journey, a partnership, a means for grown, a refuge, a bond, a joining together, and so on. What counts as a difficulty in the marriage is defined by the metaphor used. Since it is rare for spouses to have the same metaphors for their marriage, and since the metaphors are fixed in the brain but unconscious, it is not surprising that so many marriages encounter difficulties.
In politics, conservatives and progressives have ideologies defined by different metaphors. Various concepts of morality around the world are constituted by different metaphors. These results show the inadequacy of experimental approaches to morality in social psychology (e.g, Haidt's moral foundations theory) which ignore both how conceptual metaphor constitutes moral concepts and why those metaphors arise naturally in cultures around the world.
Even mathematical concepts are understood via metaphor, depending on the branch of mathematics. Emotions are conceptualized via metaphors that are tied to the physiology of emotion. In set theory, numbers are sets of a certain structure.
On the number line, numbers are points on a line. "Real" numbers are defined via the metaphor that infinity is a thing; an infinite decimal like pi goes on forever, yet it is a single entity — an infinite thing.
Though conceptual metaphors have been researched extensively in the fields of cognitive linguistics and neural computation for decades, experimental psychologists have been experimentally confirming their existence by showing that, as circuitry physically in the brain they can influence behavior in the laboratory. The metaphors guide the experimenters, showing them what to look for. Confirming the conceptual metaphor that The Future Is Ahead; The Past is Behind, experimenters found that subjects thinking about the future lean slightly forward, while those thinking about the past lean slightly backwards. Subjects asked to do immoral acts in experiments tended to wash or wipe their hands afterwards, confirming the conceptual metaphor Morality Is Purity. Subjects moving marbles upward tended to tell happy stories, while those moving marbles downward tended to tell sad stories, confirming Happy Is Up; Sad is Down. Similar results are coming in by the dozens. The new experimental results on embodied cognition are mostly in the realm of conceptual metaphor.
Perhaps most remarkable, there appear to be brain structures that we are born with that provide pathways ready for metaphor circuitry. Edward Hubbard has observed that critical brain regions coordinating space and time measurement are adjacent in the brain, making it easy for the universal metaphors for understanding space in terms of time to develop (as in "Christmas is coming" or "We're coming up on Christmas.") Mirror neuron pathways linking brain regions coordinating vision and hand actions provide a natural pathway for the conceptual metaphor that Seeing Is Touching (as in "Their eyes met").
Conceptual metaphors are natural and inevitable. They begin to arise in childhood just by living in the everyday world. For example, a common conceptual metaphor is Events with Causal Effects Are Actions by a Person. That is why the wind blows, why storms can be vicious, and why there is religion, in which the person causing those effects is called a god, or God if there is only one. The most common metaphors for God in the Western traditions is that God is a father, or a person with father-like properties — a creator, lawgiver, judge, punisher, nurturer, shepherd, and so on — and that God is The Infinite: the all-knowing, all-powerful, all-good, and first cause. These metaphors are not going to go away. The question is whether they will continue to be taken literally.
Those who believe, and promote the idea, that reason is not metaphorical —that mathematics is literal and structures the world independently of human minds —are ignoring conceptual metaphor and encouraging false literalness, which can be harmful.
The science is clear. Metaphorical thought is normal. That should be widely recognized.
Every time you think of paying moral debts, or getting bogged down on a project, or losing time, or being at a crossroads in a relationship, you are unconsciously activating a conceptual metaphor circuit in your brain, reasoning using it, and quite possibly making decisions and living your life on the basis of your metaphors. And that's just normal. There's no way around it!
Metaphorical reason serves us well in everyday life. But it can do harm if you are unaware of it.