It is a cardinal principle that all knowledge is from the Creator. Humans can get it in a passive way from revelations or in an active way by empirical observation and experimentation.

INNATE AND ACQUIRED KNOWLEDGE:

Humans have some knowledge even before birth. A human baby has limited in-born knowledge that is mostly needed for the intuitive and instinctive biological functions needed for survival at that tender age. Most human knowledge is learned. The learning can take place at the level of the individual or the community.

THREE SOURCES OF KNOWLEDGE

Revelation, reason, and empirical observation of the universe are the three major sources of acquired knowledge. Humans throughout history have quenched their thirst for knowledge from all the three sources. In terms of quantity, empirical knowledge comes first. In terms of quality revealed knowledge comes first. There is close interaction and inter-dependence between revelation, inference, and empirical observation. Reason is needed to understand revelation and reach conclusions from empirical observations. Revelation protects reason from mistakes and provides it with information about the unseen. Reason cannot, unaided, fully understand the empirical world.

EMPIRICAL OBSERVATION AS A SOURCE OF KNOWLEDGE

THE UNIVERSE IS A SOURCE OF KNOWLEDGE: The universe or cosmos around humans is a source of knowledge. Humans were given senses to enable them get empirical knowledge from their environment.

THE CONCEPT OF CAUSALITY: The concept of causality underlies most knowledge obtained by empirical observation. Simply stated this concept asserts that there is a material cause for every physical event that a human observes. He may be or not be aware of the cause but can not deny its existence.

INTELLECT AS A SOURCE OF KNOWLEDGE

INTELLECT AS A TOOL OF KNOWLEDGE: Intellect distinguishes humans from other living things on earth. It enables them to understand and correctly interpret the sensory perceptions. Intellect is so important that its misuse or under-use are severely condemned. Intellect can be a primary source of knowledge in a few instances like mathematical knowledge. In most cases the intellect is not in itself a primary source of knowledge. It is a tool that enables humans to generate deeper knowledge and understanding from the primary sources: revelation and empirical observation. Reason can be looked at as a series of intellectual processes.

INTELLECTUAL PROCESSES INVOLVED IN KNOWLEDGE: The most often referred to intellectual process is that of thinking. Thinking is closely related to empirical observation using the human senses. Thinking can be by looking. Humans are ordered to look at the cosmos and at themselves. Humans are enjoined to think about creation and its signs. Understanding is part of the thinking process. The thinking process can be extended backward in time by thinking about history and the lessons garnered from it. 

DEDUCTIVE and INDUCTIVE LOGIC: Basic analytical intellectual processes can be deductive or inductive. They are used either in parallel or in sequence depending on the problem being tackled. Induction tends to dominate in the sciences.

CONTROVERSIAL SOURCES OF KNOWLEDGE

INSPIRATION: Knowledge can be inspired. It seems that humans before birth receive knowledge about right and wrong by inspiration. Inspiration however cannot be a basis for enjoining or prohibiting actions. Inspiration cannot be accepted as evidence in law. The results of inspiration are not always consistent. We however cannot deny the possibility of some humans being inspired.

INTUITION: Intuitive knowledge is most likely part of empirical knowledge that is stored in the human subconscious and is retrieved and used on given occasions.  Humans and animals have instinctive knowledge at birth. For example nobody teaches a newborn how to suck at the mother's breast. Animals rely more on instinctive knowledge than do humans. Humans have less need for instinct because of their highly developed cerebral cortex that has more flexibility in facing and solving problems.

GEOMANCY: Geomancy is a discredited science today. It assumes ability of a human to adduce knowledge of a person’s character by incomplete observation for example looking at a person’s face and deducing what type of character he has or what experiences he has gone through. This is an unscientific approach that could lead to wrong or even dangerous conclusions. There is no empirical proof of its validity as a source of knowledge.

DREAMS: Views about the truth of dreams fall into two extremes. Materialists deny dreams whereas others believe in them and spend efforts interpreting them so that they can rely on them as sources of knowledge, guidance, and information. The truth is between the two extremes.

INVALID SOURCES OF KNOWLEDGE

SORCERY: The term sorcery is used to refer to use of magical tricks with additional psychological conditioning that can lead to real psychological effects in people who believe that they are victims of sorcery; there are no effects on those who do not believe the superstition.

MAGIC: Magic refers to use of tricks to create visual or other types of illusions. The uninitiated may be misled into believing in the existence of supernatural power because of the illusions.

ASTROLOGY: Astrology is the magical forerunner of the modern science of astronomy. Astrologers pretend to predict events in a person's life by studying the movement of stars.