Most scholars regard The Theory of Human Nature as Hume's most important work and one of the most important works in the history of philosophy, but it didn't get much attention when it was first published. When recording his lack of public attention at that time, Hume wrote: "The media's response to this book was silent, and even those enthusiastic readers did not get any explanation. But I have developed an optimistic and cheerful personality, and soon stood up from such setbacks and continued to study hard in the countryside. " He continued to write the abstract of The Theory of Human Nature, but did not write his own name. He tried to shorten and streamline his previous novels to attract more readers, but even after such efforts, he still failed to regain the importance of this book. The arduous process of writing The Theory of Human Nature made young Hume almost insane. In order to restore normal thinking ability, Hume decided to return to ordinary life temporarily. After the publication of 1744' s collection of essays "Morality and Politics", Hume applied to be a professor in the Department of Ethics and Spiritual Philosophy of Edinburgh University, but was rejected by the university. During the James Party rebellion in 1745, Hume became the governess of Marquis Annadale (1720- 1792), and was described as a "madman" by officials at that time. The job ended after only a year or so. However, it was also during this period that Hume began to write his historical masterpiece "History of Great Britain", which lasted for 15 years and exceeded one million words. Finally, it was published in six volumes from 1754 to 1762. During this period, Hume attended the Carnot Gate Theatre founded by james burnett, and he also met many other Scottish enlightenment philosophers who were in Edinburgh at that time. From 1748, he served as the secretary-general of General St. Clare for three years, and at the same time wrote his book "Inquiry into Human Understanding". However, like previous books, this book was not taken seriously when it was published at that time. At this time, Hume was accused of heresy by the church, and a young friend of Hume stood up and defended him, thinking that Hume, as an atheist, was not within the jurisdiction of the church. Although Hume was later acquitted, the University of Glasgow still rejected Hume's application as a professor of philosophy, which may also be due to another philosopher Thomas Reid's strong criticism of Hume's metaphysics. According to Hume's autobiography, it was not until 1752 that he returned to Edinburgh, "Edinburgh University asked me to be the librarian of their library. This position only earned a small salary, but it gave me the opportunity to contact such a huge library. " The rich resources in the library of Edinburgh University enabled Hume to continue his research on the history of Great Britain. Hume eventually became a famous critic and historian. His magnum opus History of Great Britain describes the history from the Saxon Kingdom to the glorious revolution, and it became a best seller as soon as it was published. In this book, Hume portrays people under the political system as products of cultural customs. Traditionally, these people tend to obey the existing government and seek change only when faced with uncertain situations. From this perspective, only religious differences can make people deviate from their daily lives and start to pay attention to political affairs. Hume's early thesis "On Superstition and Religion" laid the foundation for almost all his later works on religious history. In Hume's time, people who want to criticize religious beliefs should be cautious. For example, just before Hume was born 15, Thomas Aikenhead, a college student aged 18, was sued by the church for criticizing Christianity as "nonsense" and was finally convicted of blasphemy and hanged. So Hume only expressed his theory tactfully, and most of them were presented in the dialogue with fictional characters. Hume didn't admit that he was the author of the theory of human nature until the year of 1776. His papers On Suicide and On Immortality of the Soul, as well as his book Dialogue on Natural Religion, were published after his death (published in 1778 and 1779 respectively), and none of these works have the names of Hume or the publishers. These arrangements made by Hume to hide his authorship also make scholars still have great disputes about whether Hume is a deist or an atheist. In any case, the rumor that Hume was an atheist at that time really hit a wall and was banned when he applied for a job. Hume once mentioned to a friend that he unexpectedly "converted" to become a Christian: on his way to supervise the construction site of his new home, he accidentally slipped into the mire while crossing a newly dried-up lake in the center of Edinburgh and was trapped there because of obesity. At this time, some fish sellers happened to pass by and saw Hume's predicament, but they quickly recognized him as a famous atheist and refused to rescue him. After Hume promised to become a Christian and was forced to read the Lord's prayer and creed in the mud, these strong fish sellers pulled him up. Hume joked to his friends afterwards that these fish girls were "the smartest theologians he had ever seen". From 1763 to 1765, Hume served as the secretary of the Earl of Hartford in Paris, where he was admired by Voltaire and was known as a celebrity in the social circle of Paris. At the same time, he also met Jean Jacques Rosso. They became good friends at first, but in the end they parted because of different ideas. Hume described his life in Paris like this: "I really often want to go back to the ordinary and rough poker club in Edinburgh … to correct and relieve so many sensory stimuli these days." Hume returned to Edinburgh and settled in 1768. /kloc-around 0/770, as the German philosopher Immanuel Kant praised Hume for awakening him from the "dogmatic nightmare", Hume's philosophical works began to gain public attention, and only after that did he gain a reputation that he had never gained in his life. James boswell visited Hume a week before his death, and Hume revealed to boswell that he really began to believe those theories that he had regarded as "the most unreasonable superstition"-that is, there would be an afterlife after death. Hume wrote an epitaph for himself: "Born in 17 1 1, died in […]-let future generations fill in the blanks." After his death in 1776, Hume was buried in the "simple Roman cemetery" arranged by him before his death, which is located on the east side of Carlton in Edinburgh, overlooking his hometown in the city. Although Hume was a philosopher in the18th century, most of the topics discussed in his works are closely related to the main debates in modern philosophy, which is quite rare compared with other philosophers of his time. Some of Hume's most influential philosophical thoughts can be summarized as follows: Causality Hume advocates that as long as one thing comes with another thing, there must be a connection between the two things, which makes the latter appear together with the former (post hoc ergo propoterhoc-it appeared after that, so it must come from here). Hume refuted this theory in "Theory of Human Nature" and later "Theory of Human Understanding". He pointed out that although we can observe that one thing comes with another, we cannot observe the relationship between any two things. According to his skeptical epistemology, we can only trust the knowledge gained from our observation. Hume believes that our concept of causality is just an idea, that is, we expect one thing to happen with another. "We don't know causality, only know that some things are always linked, and these things have never been separated in past experience. We can't see through the rationality behind the connection of these things. We can only observe these things themselves and find that these things are always classified by our imagination through a frequent connection. " (Hume, 1740: 93) Therefore, we can't say that one thing makes another. We only know that one thing may be related to another. Hume put forward the word "constant combination" here, which means that when we see that one thing always "causes" another thing, what we see is actually that one thing always "frequently contacts" with another thing. Therefore, we have no reason to believe that one thing does cause another thing, and these two things may not always be "linked" in the future (popkin &: 1993: 268). The reason why we believe in causality is not because causality is the essence of nature, but because of our psychological habits and human nature (popkin &; Amp ramble, 1993: 272). Hume's statement strongly refutes causality. Some philosophers after Hume, such as Bertrand Russell, completely abandoned the concept of causality and only regarded it as a superstition. But there is also the question of causality-where does our knowledge about causality come from? What kind of connection can we recognize? There is still no clear answer to this question. Hume claimed that human beings (and other animals) have an instinct to trust causality, which comes from the habits formed in our nervous system. We can't get rid of this habit for a long time, but we don't have any arguments, and we can't prove that this habit is correct through deduction or induction, just as we know nothing about places outside the world. It is worth noting that although the theory of "frequent contact" is generally considered to be put forward by Hume, other philosophers may have put forward similar concepts long before Hume. Medieval philosopher Maimonide quoted several Islamic philosophers who also didn't believe in causality. He wrote in the book A Guide to Confused People: "In short, we shouldn't say that' this' is the reason for' that'." From the point of view of these Eslain philosophers, everything created by the creator is independent and unconnected, so there is no certain connection between these things. In On Human Understanding, Hume believes that all human thinking activities can be divided into two types: the pursuit of "conceptual relationship" and "factual problems". The former involves abstract logical concepts and mathematics, mainly intuitive and logical deduction; The latter focuses on the study of the real world. In order to avoid being influenced by any actual truth we don't know or facts we didn't perceive in past experience, we must use inductive thinking. The principle of inductive thinking is to assume that our past behavior can be a reliable guide to our future behavior (this is sometimes called natural consistency). For example, if according to past experience, the sun always rises in the east and sets in the west, then inductive reasoning will tell us that the sun may still rise in the east and set in the west in the future. But how do we explain our ability to make such inferences? Hume believes that it is impossible for us to interpret our thinking ability as the product of rationality, because rationality can only come from two ways, and neither of them can be used as the basis of our reasoning thinking: argument or intuition: such thinking is basically transcendental, and we can't prove that the future will be consistent with the past with transcendental knowledge, because the obvious fact that can be thought out (logically) is that the world is no longer consistent. Hume did not clearly distinguish between the general principle of natural consistency and a "concrete" principle of consistency here. A philosopher may argue (or maybe it is a Kantian school) that it is really hard for us to imagine that the world does not run in a "definite" form; But Hume's key point here is that even any "specific" unified principle in natural operation may stop running in the future. Therefore, inductive thinking cannot be based on transcendental knowledge. Nor can we resort to the successful experience of inductive reasoning in the past to prove the reliability of inductive reasoning, because it will constitute a circular argument. Hume went on to conclude that our thinking ability does not have a rational basis, because no form of rationality can prove such ability. It should be noted here that Hume is not advocating the following points: he is not advocating that induction is unreasonable because it does not belong to deduction (Hume is not a so-called "deductionist"). As Hume said in the section "On Skepticism and Reason", he argued that if reason can form our thoughts without foundation, and if thoughts are made up of reason from beginning to end, then we can't believe anything at all, including any truth derived from intuition or deduction. In addition, Hume does not advocate that induction is infeasible, nor does he think that induction cannot draw reliable conclusions. On the contrary, Hume argues that this inductive thinking is not actually composed of reason. Another key point of Hume's theory is that although Hume is pessimistic about the possibility that induction belongs to rational thinking, he still believes that inductive reasoning has an excellent and magical ability to foresee the future. In order to solve the problems we face in understanding inductive reasoning, Hume put forward "nature" as the answer to the problem. Nature determines that there will be more similar things we expect in the future, and "this way of thinking allows us to infer possible results through the same reasons, and vice versa." This way of thinking is an indispensable condition for all human beings to survive in the world. But we can't believe the wrong inference made by our reason, which is not only dull in thinking, but also very easy to make mistakes in our lives since we were born (On Human Understanding, 5.2.22). Hume's statement is probably the closest to the theory of evolution about human inductive thinking ability in that era (pre-Darwin era). Hume also highlights the main differences between himself and all atheist thinkers here, and presents his side as a naturalist thinker completely. Hume pointed out that we usually assume that we are the same as five years ago, although we have changed in many ways. We were the same person five years ago and now. We also think about how much time can change a person's heart without changing ourselves. However, Hume denied that there are differences between the mysterious self and a person's various personalities. When we begin to introspect, we will find: "we can never have any consciousness unless we rely on some kind of feeling;" "People are just a collection or package of many different feelings, and these feelings always alternate with each other at an unimaginable flow speed." Obviously, in the process of our thinking, our thoughts are always changing, and our imagination can easily change from one idea to another similar idea, and the characteristics of the idea itself are enough to form connections and associations. Similarly, our feelings are bound to change constantly, and the changed feelings will be similar to those before. Imagination must be a way of thinking cultivated through long-term habits, and constantly come up with new ideas with the changes of space and time. It is worth noting that from Hume's point of view, these feelings belong to nothing. On the contrary, Hume compared the human soul to a harmonious country. This harmonious country does not rely on any permanent core idea, but relies on various different, ever-changing and interrelated ideas to maintain its ontology. Therefore, the individual's noumenon is just a loose connection composed of a person's various personal experiences. In a word, for Hume, it is not important whether "ontology" exists, but the causal relationship, serial relationship and similarity between various meanings.