Recently, two friends in quick succession referred their own sick friends to me. These two friends, both of whom were my childhood and teenage playmates or classmates, heard that I was a “psychiatrist” or professor, and brought me two neurological patients who had been diagnosed in local hospitals but had poor outcomes. After taking a medical history and a brief neurological physical examination, combined with the medical records and imaging data they brought, I agreed with their previous diagnosis of neurology and told them that this was not a disease I was good at treating, and suggested that they continue to be seen and treated in neurology. Faced with their puzzled eyes, I briefly explained the difference between “neurology” and “psychosis”, and they realized that I was a specialist in treating psychosis rather than neurology. When it comes to the difference between neurosis and psychosis, a few years ago, most non-medical professionals did not know the difference between the two. Even today, there are many people who would think that the two are probably the same thing. In this article, I would like to sort out the similarities, differences, and associations between the two, as a kind of science article on the concept of these two types of diseases. From the point of view of the disease classification system of clinical medicine, there are two major categories of diseases directly related to the nervous system, one is neurological diseases and the other is psychiatric diseases, which are intrinsically different from each other and inextric links. To use a more graphic analogy, if we consider the human body as a complex computer system with many important peripheral devices, the nervous system is the hardware part including input and output devices and connecting wires inside and outside the computer, while the central nervous system is equivalent to the mainframe of this computer, and the mental activity is the software part including the operating system and various applications in the mainframe of this complex computer system. This computer system may experience both hardware damage and abnormal software functions. If damage occurs to this system either to the hard disk, central processor, monitor or memory of the mainframe, or to the peripheral keyboard, mouse or even wires, it is a neurological disorder. For example, brain hemorrhage, encephalitis, peripheral neuritis, etc., are neurological diseases. It can be simply understood that neurological diseases mainly involve structural or so-called “organic” abnormalities that manifest as damage to human sensory (sensory loss) or motor functions (limb paralysis), or “hardware” failures. Of course, specific hardware damage that performs certain software functions can also be accompanied by corresponding software functional deficits, such as diffuse brain damage in encephalitis that is inevitably accompanied by abnormalities in the mental functions of the brain. Conversely, if the hardware of the system is intact, but only its operating system or the degree of application starts or runs out of order and cannot properly perform the corresponding function or task, it is a psychiatric disorder. For example, depression, anxiety and psychotic disorders with hallucinatory delusions, these are psychiatric disorders. It can also be simply understood that mental activity abnormalities without structural damage to the nervous system are psychiatric disorders, which are “software” failures. Although neurological disorders are theoretically hardware failures and psychiatric disorders are software failures, there is an interconnection and influence between them. That is, neurological diseases, especially central nervous system diseases, especially cranial diseases, are often accompanied by corresponding psychiatric disease manifestations. For example, trauma or damage to the cerebral cortex may result in definite psychiatric abnormalities, typical cases being psychiatric abnormalities and personality changes after bilateral frontal lobe penetrating injuries to the brain, intellectual impairment and other psychiatric abnormalities in patients suffering from cerebral syphilis. Conversely, software problems may also bring about hardware changes, as in the case of many patients with psychiatric disorders of long duration and persistent unremitting disease, where brain imaging reveals a reduction in the size of certain brain structures. In terms of disease prognosis, there is still an important difference in the probability of cure between the two types of disorders. Still using the computer as an analogy: for a computer system, a hardware failure that cannot be replaced with a matching accessory will result in a corresponding loss of function or damage. Since a complex organism such as the human body cannot be replaced with “original” parts, those tissues, structures and even cells (neurons or glial cells) that are irreversibly damaged in neurological diseases will lose or lose the functions they perform. Even if, through certain repair and compensatory mechanisms, the functions performed by the damaged tissues and structures improve or recover after the acute phase of these diseases, it is almost impossible to fully restore them to their pre-morbid level or state. In contrast, if a computer has a software failure, such as a software “bug” (an error or vulnerability in a computer program), the “bug” can be completely repaired by modifying the software. In the case of a software failure or even a crash of the operating system of the human central nervous system, i.e., a mental illness, it is theoretically possible to cure it completely if the most appropriate treatment strategy and treatment plan can be found. Even certain recurrent mental illnesses may be cured each time after systematic and standardized treatment. However, due to the limitations of the level of development of psychiatry, we have not yet found a cure for every psychiatric disorder, but we can indeed look forward to that day.