Ludwig Wittgenstein (1889 - 1951)

Considered by some to be the greatest philosopher of the 20th century, Ludwig Wittgenstein played a central, if controversial, role in 20th-century analytic philosophy. He continues to influence current philosophical thought in topics as diverse as logic and language, perception and intention, ethics and religion, aesthetics and culture. 

There are two commonly recognized stages of Wittgenstein's thought — the early and the later — both of which are taken to be pivotal in their respective periods. 

The early Wittgenstein is epitomized in his Tractatus Logico-Philosophicus. By showing the application of modern logic to metaphysics, via language, he provided new insights into the relations between world, thought and language and thereby into the nature of philosophy. 

It is the later Wittgenstein, mostly recognized in the Philosophical Investigations, who took the more revolutionary step in critiquing all of traditional philosophy including its climax in his own early work. The nature of his new philosophy is heralded as anti-systematic through and through, yet still conducive to genuine philosophical understanding of traditional problems.

Immanuel Kant (1724–1804)

Is the central figure in modern philosophy. He synthesized early modern rationalism and empiricism, set the terms for much of nineteenth and twentieth century philosophy, and continues to exercise a significant influence today in metaphysics, epistemology, ethics, political philosophy, aesthetics, and other fields. The fundamental idea of Kant's “critical philosophy”. 

He argues that the human understanding is the source of the general laws of nature that structure all our experience; and that human reason gives itself the moral law, which is our basis for belief in God, freedom, and immortality. Therefore, scientific knowledge, morality, and religious belief are mutually consistent and secure because they all rest on the same foundation of human autonomy, which is also the final end of nature according to the teleological worldview of reflecting judgment that Kant introduces to unify the theoretical and practical parts of his philosophical system.

Spinoza (1632 - 1677)

       Spinoza is one of the most important philosophers—and certainly the most radical—of the early modern period. His thought combines a commitment to Cartesian metaphysical and epistemological principles with elements from ancient Stoicism and medieval Jewish rationalism into a nonetheless highly original system. His extremely naturalistic views on God, the world, the human being and knowledge serve to ground a moral philosophy centered on the control of the passions leading to virtue and happiness. They also lay the foundations for a strongly democratic political thought and a deep critique of the pretensions of Scripture and sectarian religion. Of all the philosophers of the seventeenth-century, perhaps none have more relevance today than Spinoza.

—His ethics are very similar to Aristotle’s in content and in being eudemonistic. 

—He holds a reductionist and arguably naturalistic understanding of the human being.

—He denies the freedom of the will and transcendent values.

—He tends to subsume the practical under the theoretical.
 

Method of Epistemology:
The admission that there are a variety of ways one can have knowledge.
There is a definitively adequate way for knowing this variety of ways.
—Spinoza’s method has two aspects; one that is formal and another that is more concerned with the concrete perspectives that define the different ways one can have knowledge. 

Knowledge — :

 Adequate vs. Inadequate ideas
3 Types of knowledge

-Imagination: disorganized accumulation of experience

- Reason : logical deductions made based on an understanding of the nature of space (e.g. geometry) or of the nature of thought (e.g. logic, psychology)

-intuition: the intuitive grasp of a particular thing on the basics of ration   

 
Ethics: 

—The polemic against traditional ethics:  

-Against free will

  -Against absolute normative terms 

  -Against teleology 

—The naturalistic replacement: 

  -The human being as conatus 

  -The redefinition of “freedom,” “good,” and “bad” 

  -A special brand of hedonism 

  -Resemblance to Aristotelian virtue ethics 

  -Akrasia and moral knowledge

William Ockham (1287 - 1347)

William of Ockham is, along with Thomas Aquinas and John Duns Scotus, among the most prominent figures in the history of philosophy during the High Middle Ages. He is probably best known today for his espousal of metaphysical nominalism; indeed, the methodological principle known as “Ockham's Razor” is named after him. But Ockham held important, often influential views not only in metaphysics but also in all other major areas of medieval philosophy—logic, physics or natural philosophy, theory of knowledge, ethics, and political philosophy—as well as in theology.

Ockham's is not much concerned with answering skeptical doubts. He takes it for granted that humans not only can but frequently do know things, and focuses his attention instead on the “mechanisms” by which this knowledge comes about.  Ockham's theory of knowledge, like his natural philosophy, is broadly Aristotelian in form, although—again, like his natural philosophy—it is “Aristotelian” in its own way. For most Aristotelians of the day, knowledge involved the transmission of a “species” between the object and the mind. At the sensory level, this species may be compared to the more recent notion of a sense “impression.”