We dream to keep our brains working.
我们为了保证大脑运转而做梦。
The continual activation theory proposes that your dreams result from your brain's need to constantly consolidate and create long-term memories in order to function properly.
持续激活理论提出，你做梦是由于你的大脑为了有效运转需要持续不断地巩固和创造长期记忆。
So when external input falls below a certain level, like when you're asleep, your brain automatically triggers the generation of data from its memory storages, which appear to you in the form of the thoughts and feelings you experience in your dreams.
因此，当外界的输入低于一个特定水平时，例如你在睡觉时，你的大脑会自动触发记忆库里的数据形成，而这些在你看来就是你在梦里的想法和感受。
In other words, your dreams might be a random screen saver your brain turns on so it doesn't completely shut down.
换句话说，你的梦也许是个大脑运转时的随机保护程序，所以大脑并不会完全停止运转。
We dream to rehearse.
我们为了预演而做梦。
Dreams involving dangerous and threatening situations are very common, and the primitive instinct rehearsal theory holds that the content of a dream is significant to its purpose.
梦经常包含危险和恐怖的情景，而原始本能理论认为梦的内容对于它的目的来说非常重要。
Whether it's an anxiety-filled night of being chased through the woods by a bear or fighting off a ninja in a dark alley, these dreams allow you to practice your fight or flight instincts and keep them sharp and dependable in case you'll need them in real life.
无论是一个在森林中被熊追着跑的紧张夜晚，还是在幽暗的山谷中击退一个日本武士，这些梦允许你锻炼战斗或逃跑的本能，而且保证万一在现实中需要它们时，能保持一定的敏锐度和可靠性。
But it doesn't always have to be unpleasant.
不过梦也不一定总是不愉快的。
For instance, dreams about your attractive neighbor could actually give your reproductive instinct some practice, too.
比如，梦到你魅力无限的邻居可能会给你的生殖本能带来一定的锻炼。
We dream to heal.
我们为了治愈而做梦。
Stress neurotransmitters in the brain are much less active during the REM stage of sleep, even during dreams of traumatic experiences, leading some researchers to theorize that one purpose of dreaming is to take the edge off painful experiences to allow for psychological healing.
压力神经传导物质在快速眼动睡眠时期会表现得非常不活跃，即使是梦到受伤的经历，这一现象导致研究人员推测梦的一个目的是减弱不好经历带来的痛苦，以达到心理治疗的目的。
Reviewing traumatic events in your dreams with less mental stress may grant you a clearer perspective and enhanced ability to process them in psychologically healthy ways.
在梦中以更小的精神压力回顾创伤性事件，可能会给你一个更加清晰透彻的看法，以及增强你积极乐观地面对它们的能力。
People with certain mood disorders and PTSD often have difficulty sleeping, leading some scientists to believe that lack of dreaming may be a contributing factor to their illnesses.
有特定情绪失常和创伤后应激障碍的人可能很难入睡，这一现象导致一些科学家开始相信，缺乏做梦可能是加重他们病情的一个因素。
We dream to solve problems.
我们为了解决问题而做梦。
Unconstrained by reality and the rules of conventional logic, in your dreams, your mind can create limitless scenarios to help you grasp problems and formulate solutions that you may not consider while awake.
不受现实生活和常规逻辑的约束，你的梦可能会产生无限的场景来帮助你把握问题，以及形成你醒着的时候完全不会考虑到的解决方法。
John Steinbeck called it the committee of sleep, and research has demonstrated the effectiveness of dreaming on problem solving.
约翰·斯坦贝克把它称为睡眠委员会，而研究人员也已证实做梦在解决问题上的有效性。
It's also how renowned chemist August Kekule discovered the structure of the benzene molecule, and it's the reason that sometimes the best solution for a problem is to sleep on it.
这也就是为什么著名的化学家奥古斯特·凯库勒发现了苯分子的结构，也是为什么有些时候解决一个问题的最好办法就是睡一觉。
And those are just a few of the more prominent theories.
这里也有一些更为突出的理论。
As technology increases our capability for understanding the brain, it's possible that one day we will discover the definitive reason for them.
当科技增强了我们理解大脑的能力之后，有一天我们有可能会发现梦存在的真正原因。
But until that time arrives, we'll just have to keep on dreaming.
但是直到那一天到来之前，我们仍旧需要不停地做梦。
