The classical school of Indian philosophy has been classified into two broad divisions. The first being the orthodox or the Astika School of philosophy and the second is the heterodox or the Nastika School of philosophy. The orthodox philosophy has bestowed its religious authority on the Vedas whereas the heterodox school has denied the supremacy of the Vedas. It is true that the schools have been segregated on the basis of their ideologies and beliefs but a common theme runs within all the schools of Indian philosophy. All the schools believe that man is a spiritual being and hence tries to relate him to the metaphysical world or to the universe as a whole. All the schools of Indian thought have related the concept of Indian philosophy very closely with the practical world. They believe that philosophy is not merely an academic discipline but it is a guide to human life. The schools of Indian thought have also given adequate focus on the essence of good life on earth. Moreover the definition of good life is similar for all them because all of them have said that good life incorporates a dedicated fulfillment of social as well as familial responsibilities.

The two classical schools of Indian Philosophy have further been classified into subdivisions. The orthodox school has been divided into six categories and the heterodox school has been classified into three sections.

Orthodox School of Indian Philosophy
The six schools of the orthodox or the Astika School include the school of logic or Nyaya, the school of enumeration or Samkhya, the atomist school or Vaisheshika, the school of Patanjali or Yoga, the school emphasizing on the Vedic ritual or the Purva Mimasa and the school following the Upanishadic tradition and focusing on the Vedic philosophy or the Vedanta.

The school of logic or Nyaya was started by one of the early saints Gautama. This school of philosophy deals with the concepts of reasoning and logic. It stresses that questioning is an absolute necessary for philosophical pursuit. Most of the other school of Indian philosophy has drawn its inspiration from this school of Nyaya. The Samkhya or the school of enumeration is the philosophy of manifestation. It includes the manifestation of all entities from the most subtle to the grossest. The main elements of this school are the mind, the matter, the cognitive senses, ahamkara, the three gunas and also the five elements including the earth, air, fire, water and space. In fact this school of Indian philosophy incorporates within itself all the elements which may be the domains of other schools of philosophy. The atomist school or Vaisheshika deals with the physical sciences of the world. This school of thought was begun by Prashastapada and focuses on the physical sciences like Chemistry. It explores the five elements and also interprets the mind and soul of living beings. Yoga or the school of Patanjali explores all the state of human existence. The school of Yoga focuses on the consciousness of human beings as the eternal center. The main aim of this school is to make man realise his inner self with the help of his consciousness. The Purva Mimasa School of Philosophy was started by Jamini. This school focuses on the emancipation of the human soul with the help of actions. The postulates of the Purva Mimasa School have laid a lot of importance on the concept of Karma and they believe that a life under the guidance of proper ritual, worship and ethical conduct leads a human soul towards emancipation. The last but not the least the Vedanta School of Indian Philosophy focuses on the concept of self-realisation which will enable man to find his true nature which is beyond any kind of decay, decomposition or death. Rather it can be said that the Vedanta School of Indian Philosophy emphasises on the discovery of the true self, a self which is timeless. The tenets of the Vedanta philosophy have been explained in the Upanishads.

These six schools are generally combined with each other in order to elucidate the concepts in a proper manner. The Mimamsa-Vedanta, Nyaya-Vaishesika and Samkhya-Yoga are grouped together in the orthodox school of Indian philosophy.

The Vedanta School on the other hand is categorized into another six subsystems. They are namely the Dvaita or dualism, Adavita or monism/ non-dualism, Dvaitadvaita or dualism-nondualism, Visisthatdvaita or monism of the qualified whole, the Achintya Bheda Abheda Schools and the Suddhavaita.

Heterodox School of Indian Philosophy
The heterodox or the Nastika School includes the philosophical tenets of Buddhism, Jainism and the Carvaka. The Buddhist Philosophy was founded by Gautama Buddha in India. The Buddhist philosophy can be classified as a non-theistic philosophy. The philosophy does not give primacy to the existence of God but focuses on the concepts of Karma, reincarnation and Moksha. The Buddhist philosophy is similar to the Hindu philosophy but in many other places it differs with the basic concepts of Hindu philosophy. The main aim of the Buddhist philosophy is to bring an end to the cycle of births and attain salvation in the process.

Mahavira had propounded the Jain philosophy in India. The basic component of the Jain philosophy was the emphasis on Anekantavada. Jain philosophy says that only the Kevalis or the ones who have achieved infinite knowledge can know the entire truth and the others have access to only a part of the truth. The Jain philosophy has largely been influenced by the concept of Subjectivism which is an integral part of the Western Philosophy.

The Carvaka School of Thought is based on the concepts of atheism and materialism. Although not a part of the six schools of philosophy within the orthodox school, the Carvika School of thought can be considered an important philosophical movement within Hinduism.

Thus it can be said that though India may have different school of philosophies yet the basic theme of all the school remains the same. All of them try to search for the truth through an inward introspection of the self. They believe that the inward self is of much importance than the physical world. Rather it can be said that the ways taken by the different schools may be different but the ultimate aim remains the same.