什么是哲学

What is Philosophy?

What is Philosophy?

Quite literally, the term "philosophy" means, "love of wisdom." In a broad sense, philosophy is an activity people undertake when they seek to understand fundamental truths about themselves, the world in which they live, and their relationships to the world and to each other. As an academic discipline philosophy is much the same. Those who study philosophy are perpetually engaged in asking, answering, and arguing for their answers to life’s most basic questions. To make such a pursuit more systematic academic philosophy is traditionally divided into major areas of study.

Metaphysics: At its core the study of metaphysics is the study of the nature of reality, of what exists in the world, what it is like, and how it is ordered. In metaphysics philosophers wrestle with such questions as:

  • Is there a God?
  • What is truth?
  • What is a person? What makes a person the same through time?
  • Is the world strictly composed of matter?
  • Do people have minds? If so, how is the mind related to the body?
  • Do people have free wills?
  • What is it for one event to cause another?

Epistemology: Epistemology is the study of knowledge. It is primarily concerned with what we can know about the world and how we can know it. Typical questions of concern in epistemology are:

  • What is knowledge?
  • Do we know anything at all?
  • How do we know what we know?
  • Can we be justified in claiming to know certain things?

Ethics: The study of ethics often concerns what we ought to do and what it would be best to do. In struggling with this issue, larger questions about what is good and right arise. So, the ethicist attempts to answer such questions as:

  • What is good? What makes actions or people good?
  • What is right? What makes actions right?
  • Is morality objective or subjective?
  • How should I treat others?

Logic: Another important aspect of the study of philosophy is the arguments or reasons given for people’s answers to these questions. To this end philosophers employ logic to study the nature and structure of arguments. Logicians ask such questions as:

  • What constitutes "good" or "bad" reasoning?
  • How do we determine whether a given piece of reasoning is good or bad?

History of Philosophy: The study of philosophy involves not only forming one’s own answers to such questions, but also seeking to understand the way in which people have answered such questions in the past. So, a significant part of philosophy is its history, a history of answers and arguments about these very questions. In studying the history of philosophy one explores the ideas of such historical figures as:

  • Plato
  • Aristotle
  • Aquinas
  • Descartes
  • Locke
  • Hume
  • Kant
  • Nietzsche
  • Marx
  • Mill
  • Wittgenstein
  • Sartre

What often motivates the study of philosophy is not merely the answers or arguments themselves but whether or not the arguments are good and the answers are true. Moreover, many of the questions and issues in the various areas of philosophy overlap and in some cases even converge. Thus, philosophical questions arise in almost every discipline. This is why philosophy also encompasses such areas as:

  • Philosophy of Law
  • Philosophy of Religion
  • Philosophy of Mind
  • Political Philosophy
  • Philosophy of History
  • Philosophy of Feminism
  • Philosophy of Science
  • Philosophy of Literature
  • Philosophy of the Arts
  • Philosophy of Language
[@more@]==== http://www.fsu.edu/~philo/new%20site/sub_category/whatisphilo.htm

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转载于:http://blog.itpub.net/37724/viewspace-1026728/

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<think>嗯,用户想了解哲学家就餐问题中的死锁条件,特别是请求与保持、不剥夺、循环等待这些概念。首先,我需要回忆一下哲学家就餐问题的基本设定。五个哲学家围坐,五根筷子,每人左右各一根。他们要交替思考和进餐,进餐时需要同时拿起左右两边的筷子。问题在于如果所有哲学家同时拿起左边的筷子,就会陷入死锁,因为每个人都在等待右边的筷子,而右边的筷子被旁边的人拿着。接下来,用户提到的死锁四个必要条件:互斥、请求与保持、不剥夺、循环等待。需要将这四个条件和哲学家问题对应起来。比如,互斥是指筷子一次只能被一个哲学家使用,这显然满足,因为一根筷子不能被两个人同时拿。请求与保持,指的是哲学家在等待另一根筷子时不会释放已持有的,这点在问题中也存在,因为他们拿着左边的筷子等待右边。不剥夺条件,资源不能被强制拿走,所以哲学家不能抢别人的筷子。循环等待,就是形成一个环路等待,比如每个哲学家都在等右边的人释放筷子,导致循环依赖。 然后,我需要参考用户提供的引用内容。引用1中提到消除循环等待的方法,比如规定拿筷子的顺序,比如奇偶编号的哲学家先拿不同方向的筷子。引用2和3也提到类似的方法,以及活锁的可能性。引用4提到使用条件变量和状态判断来避免死锁,比如只有当左右邻居都没进餐时才能拿筷子。现在需要把这些信息整合成清晰的回答,分点解释每个死锁条件在哲学家问题中的体现,并给出解决方案,比如破坏循环等待的方法。同时,用户要求生成相关问题,可能需要包括如何预防死锁、活锁与死锁的区别,或者具体的算法实现等。 需要注意的是,用户可能混淆了死锁的四个必要条件,需要明确区分。比如,互斥是资源本身的特性,而请求与保持是进程的行为。在回答时要准确对应每个条件,并举例说明。同时,引用中的例子要自然地融入回答,并正确标注引用标记,比如[^1]、[^2]等。最后,生成的相关问题应该围绕死锁的条件、解决方案、实际应用等展开,帮助用户进一步理解。例如,如何破坏请求与保持条件,或者比较不同死锁预防方法的优劣。</think>### 哲学家就餐问题与死锁条件分析 哲学家就餐问题是操作系统领域描述死锁的经典模型。当所有哲学家同时拿起左侧筷子时,系统会进入死锁状态。以下结合死锁的四个必要条件进行解释: #### 1. **请求与保持(Hold and Wait)** 哲学家在拿起一根筷子后,会**保持持有状态**,同时**请求另一根筷子**。例如,当哲学家A持有左侧筷子时,会继续请求右侧筷子,此时既不释放已有资源,也不放弃请求新资源[^1]。 #### 2. **不剥夺(No Preemption)** 筷子资源**不可被强制剥夺**。若哲学家B持有右侧筷子,其他哲学家无法强行抢夺,只能等待其主动释放[^1]。 #### 3. **循环等待(Circular Wait)** 哲学家之间形成**环形依赖链**:哲学家1等待哲学家2的筷子,哲学家2等待哲学家3的筷子,依此类推,最终哲学家5等待哲学家1的筷子,构成闭合环路[^3]。 #### 4. **互斥(Mutual Exclusion)** 每根筷子**同一时间只能被一个哲学家使用**,这是资源本身的特性决定的[^4]。 --- ### 破坏死锁的典型方法 #### 方法1:破坏循环等待条件 通过**规定资源请求顺序**消除环形依赖: - 奇数编号哲学家先拿左侧筷子,偶数编号先拿右侧筷子[^2]。 例如:哲学家1(奇数)先拿左边筷子1,哲学家2(偶数)先拿右边筷子3,避免形成全局环形竞争。 #### 方法2:破坏请求与保持条件 要求哲学家**一次性获取所有资源**: - 使用信号量机制,仅当左右筷子均可用时才允许拿起[^4]。 #### 方法3:引入超时机制(破坏不剥夺条件) 若等待超过阈值(如5分钟),则主动释放已持有的筷子[^3]。但此方法可能引发活锁(哲学家反复同步释放资源)。 --- ### 示例代码(破坏循环等待) ```python class Philosopher: def __init__(self, id, left, right): self.id = id if id % 2 == 1: # 奇数号先左后右 self.first = left self.second = right else: # 偶数号先右后左 self.first = right self.second = left def eat(self): with self.first: # 按顺序获取资源 with self.second: print(f"Philosopher {self.id} is eating") ``` ---
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