怀疑论问题是知识论研究中最为困难的议题之一，也是一切哲学研究必须面对的重要问题之一。当代怀疑论主张，我们没有任何知识，我们不能够完全相信任何信念都是真的。面对怀疑论的挑战，知识论者提出了各种反怀疑论论证，但都被认为存在弊病。德性知识论的首倡者欧内斯特·索萨持坚定的反怀疑论立场，并提出独具特色的反怀疑论方案。本文以索萨的德性知识论为主题，以当代知识论中的怀疑论论证为背景，完整呈现了索萨的两种反怀疑论论证，构建了一种综合的梦境想象模型，以修补索萨式梦境想象模型的理论缺陷，创新性地论证了一种德性证成理论，即以德性为知识证成的基础，以安全性条件与德性条件的实用融合为关键，为反怀疑论提供一种更为可行的德性路径。

德性路径是对内在主义路径的回归与超越。其基本思路是，解决怀疑论问题的关键在于如何非循环地解释证成来源是可靠的。其中，胜任力可靠性的德性解释与论证是德性路径的核心和关键。默认假设理论则是专门处理认知胜任力可靠性的理论。根据该理论，我们可以默认胜任力正常运行的背景条件始终在场，从而确保胜任力始终可靠。即使我们身处怀疑论场景，也可以假定“我们知道非SH”，即我们并非身处怀疑论场景之中，从而拒斥怀疑论。但这种反怀疑论回应会引起两个反直觉争议，一是反闭合原则的争议，二是反认知证成的争议。本文认为，反闭合原则的争议不是默认假设理论的真正争议所在，可以被消解掉；真正的争议是索萨将实用因素引入知识论，引起了一种反认知证成的争议，产生了实用侵入问题。

正统观点认为，知识证成只是一种认知证成而非实用证成，换言之，决定我们是否知道的是认知因素而非实用因素。本文认为，索萨为实用侵入提供了一种可行的德性解释。两种反怀疑论方案是关于知识的两种证成条件：安全性条件基于一种反运气直觉，主张知识必须排除运气成分；德性条件基于一种能力直觉，主张知识的获得源自认知能力的恰当运行。这两种证成条件在竞争中以一种实用主义方式相互融合，体现了索萨知识论的美国哲学特色，为实用侵入提供了一种德性解释，也为解决怀疑论问题提供了德性的实用证成新尝试。在当代知识论背景下，实用侵入在知识论中占有一席之地，实用因素在很大程度上影响我们是否知道某事，并在反怀疑论问题上发挥重要作用。

总之，本文从知识证成问题出发，以索萨对怀疑论问题的德性知识论解答为中心，最后回到知识证成问题。本文的最终目的，是为解决怀疑论问题提供一种更为可行的德性证成路径，力图在知识与怀疑之间架构起一座德性证成之桥，使得我们从怀疑走向确定的知识彼岸。

Skepticism is one of the most difficult issues in epistemology, and one of the important problems that all philosophical research must face. Contemporary skepticism claims that we do not have any knowledge, that we can't be completely convinced that any belief is true. Faced with the challenge of skepticism, epistemologists put forward various anti-skepticism arguments, but all of them are considered flawed. However, Ernest Sosa, the pioneer of virtue epistemology, held a firm position of anti-skepticism and put forward the unique anti-skepticism scheme. This paper takes Sosa's virtue epistemology as the theme, the contemporary skeptical argument t as the background, to thoroughly and critically analyzes two anti-skepticism arguments by Sosa, to construct a comprehensive imagination model of dreaming, to repair Sosa’s imagination model of dreaming theoretical defects, and to demonstrate a novel idea of virtue justification. It provides a more feasible virtue approach for anti-skepticism by taking virtue as the basis of knowledge justification and the practical fusion of safety condition and virtue condition as the key.

    The virtue approach is a return and transcendence to the externalism. The basic idea is that the key to solve the problem of skepticism lies in how to explain the reliability of the sources of evidence acicularly. Among them, the reliability description of competency is the core and key of The Sosa approach. The default assumption theory deals specifically with the reliability of cognitive competence. According to this theory, we can ensure that the competency is always reliable by default by running the background conditions required to always be in place. Thus, even though we are likely to be in a skeptical scenario, we can assume that "we know not to be SH" that we are not in a skeptical scenario and reject skepticism. This anti-skeptical response will give rise to two counter-intuitive controversies, one is the controversy over the anti-closure principle and the other is the controversy over the anti-cognitive justification. This paper argues that the controversy of the anti-closure principle is not the real controversy of the default assumption theory and can be resolved. The real controversy is that Sosa introduces the practical factor into the theory of knowledge, causing controversy of anti-cognitive justification, resulting in the problem of pragmatic encroachment.

    The orthodox view is that knowledge can only be a cognitive rather than a practical justification, that is, it is cognitive rather than practical factors that determine whether we know or not. This paper argues that Sosa provides a feasible explanation of virtue for pragmatic encroachment. The two anti-skeptical schemes he provides are two kinds of justification conditions about knowledge: The safety condition is based on an anti-luck intuition, which advocates that knowledge must exclude the luck component in knowledge. The virtue condition is based on a kind of ability intuition, which holds that the acquisition of knowledge comes from the proper operation of cognitive competence. This paper argues that these two kinds of justification conditions merge with each other in a pragmatic way in the competition, which embodies the American philosophical characteristics of Sosa's epistemology, provides a kind of explanation of virtue for pragmatic encroachment, also provides a new attempt to solve the problem of skepticism. In the context of contemporary epistemology, pragmatic encroachment has a place in epistemology. Pragmatic factors influence whether we know something to a great extent and play an important role in anti-skepticism.

    In a word, this paper starts from the justification problem of knowledge, takes Sosa's virtue answers to the skeptical problem as the center, and finally returns to the knowledge justification problem. The goal of this paper is to provide a more feasible path of virtue justification to solve the skepticism. By establishing a bridge between knowledge and doubt, this paper tries to make us move from doubt to certainty.