Philosophy can be divided into two major directions of thought, centered on what is considered to be the fundamental issue in philosophy: the relation between Being and Thinking. In this short discussion I will try to briefly explain these two major directions in philosophy. Let us consider some very basic feauture of our being. We sit for instance on a chair. We can see the chair, we can touch it, and the other senses can as well perceive of the chair. Now these perceptions all occur within our brain, where the input data of the sensory organs come together, and form an "image" of the thing we perceive. A central issue in this is wether or we regard the thing that caused the perceptions as real or not. Or in other words, apart of our perceptions and awareness of the chair, is there realy something outside and seperate from our mind? Materialism answer this with a clear yes. Not only by our senses but also through science and instruments, we can know about this object, that is seperate from out mind. There is an objective world, independend of our mind. The objective world consists of what is called matter, which has the property of being in motion (undergoing change) at all time. Space and time just denote the modes of existence of matter. Idealism answers this with a clear no. Apart from our immediate perceptions and awareness of the world, there is no such thing as an outside, objective world. The world takes places entierly within our mind. Outside of that, nothing exists. So, these opposing philosophies contradict each other in their definition of what the world is consisting of in primary instance. Materialism claims that in first instance the world is just matter in motion. Our mind, brain and body only denote a specific form of matter. So, our mind, awareness and thoughts, are a secondary property of matter. Idealism on the other hand claims that there is no such material world, and that the world in first instance is our mental process, our mind and thoughts. That what is perceived, and which behaves ordinary, is not an entity on itself, but was created in or by the mind. If we consider the claim of Idealism to it's ultimate extend, we conclude that it would see on the world as if there was only one mind. This would lead to to contradictionary point of view of solipsism, which is the vision that apart from our individual mind, nothing at all whatsoever exists, including other minds. This point of view of solipsism is however not a viewpoint taking in by any known philosopher. It would be a contradictiong thing to consider it even a philosophy, cause the actrivity of philisophy contains discussing it with other people (minds). According to solipsism, only one such mind exists, so to discuss it with other minds would be a contradiction in terminio. Idealism however, in order to escape from this absurd point of view, is more commonly known and developed in the form of objective idealism. Instead of one individual mind, the world is considered to be in essence and primary instance an Absolute Idea (Hegel) or fundamental principle. The connection between objective idealism and religion can be made clear, cause the idea of a deity (God) is just that: a fundamental principle or Absolute Idea. Idealism as such as a whole does not oppose as such the fact that there is a material world, only that in the point of view of idealism, matter is not the primary substance. According to idealism mind (Hegel: Geist) in the form of a fundamental principle or an Absolute Idea is the primary substance, matter is just a secondary substance, which does not exists independend of mind. The philosophy of materialism and idealism not just oppose each other on the issue of what is the primary substance the world is made of, but also about the issue if and how the world can be known. Materialism claims that the world in knowable. Through science we have been able to acquire a lot of knowledge, and science will ever progress. Materialism rejects the idea of absolute knowledge. Science can improve our knowledge, but can not find the ultimate or absolute truth. Knowledge progresses through relative knowledge, that create a gradual improving and more 'realistic' picture of the outside, objective, material world. The way we gain more knowledge is by doing experiments, verify theories, explore the material world, etc. The building of theories follows the experiment and observation. We cannot have prior knowledge about the world, before exploring it, and no scientific theory can be claimed to be true, if it can not be stated on experiment and/or observation. Idealism claims that we cannot know about the world. According to idealism the world is based on a fundamental principle or Absolute Idea. The way in which idealism progresses in order to gain knowledge, is to theoretize, debate and discuss ideas, which reflect on the fundamental principle of nature or the Absolute Idea. In current day science we can still see the struggle between these opposing philosophies, and in the emergence of contemporary theories in the field of physics and cosmology. Consider for instance string cosmology/M theory, or the idea about a "beginning of time", which are nothing more as reflections on some (unknown) fundamental principle or Absolute Idea, which is thought as to be the essence of nature. On the other hand, based on materialism and the progress of science in many fields, we can witness the fact that mankind gathered a lot of knowledge in the past couple of hundred years. For instance we have a profound understanding (but still incomplete) how natural processes were causing evolution and how it still works today, we have a profound understanding of the physical laws of the universe and the origin of the cosmos (special realtivity, general relativity, quantum mechanics, uncertainty principle, quantum chromo dynamics, expansion of the universe, etc), although we know we don't have and never will have a complete understanding.