At the outset, philosophical thought hinges on sense-perception, later it rises to rational considerations, and finally roots itself in spiritual experience. The Nyaya and the Vaiseshika systems base themselves mainly on the logic of inference and consider, principally, perception, inference and verbal testimony as the valid means of acquiring right knowledge. Perception and inference conclude that the entire creation is composed of nine substances, namely, Earth, Water, Fire, Air, Ether, Time, Space, Soul and Mind, though all the elements enumerated, except Mind and Soul, can be regarded as objects of direct perception through the senses. Mind and Soul could also be regarded as existence through inferential knowledge. The gross elements, namely, Earth, Water, Fire and Air, are reducible to atoms that combine themselves into the very objects in creation. Apart from one of the five elements, i.e., Ether, the principles of Space and Time are to be regarded as abstract realities to make any sense out of the process of creation as a reality at all. Mind and Soul give meaning to individuality, or the very existence of the person.

How could atoms combine themselves into forms unless there is an arranger of atoms into the requisite forms? The existence of God as the fashioner of all creation has logically to be accepted, without which position the creation of the world cannot be adequately accounted for, and also there would be no ground for the dispensation of justice in respect of the good and the bad deeds of individuals. For this reason, and many others of this kind, the existence of God is to be accepted. God, as the fashioner of all things of which the world consists, has naturally to be outside creation, extra-cosmic in nature, since one who is involved in the very substance of creation cannot be regarded as its creator. Further, from the point of view of the individuals, it is to be concluded that knowledge arises by the contact of the soul with mind in perception, and such knowledge will not be present when 'the mind is dissociated from the soul, as in the state of salvation achieved through freedom from desire and unselfish action.

The Samkhya system examines the Nyaya and the Vaiseshika position and feels that it is not possible to categorise the substance of creation into neat packets with no internal relation among them, because an internal coherence of the parts of a whole is implied in the organic and unified manner in which the world works. An extra-cosmic God would not solve this problem, since that which is outside the cosmos cannot touch the cosmos and such a God cannot even be regarded as having a hand in creation. God's extra-cosmic position would prevent his hands from reaching creation. The Samkhya posits only two realities, namely, Prakriti and Purusha, in place of the categories of the Nyaya and Vaiseshika, which stand for matter and spirit in their general connotation. There are only two things that are seen to be operating everywhere, that is, a consciousness that knows and matter that is known. We cannot think of a third element anywhere other than these two eternal principles. The process of knowledge is an interaction between consciousness and matter, Purusha and Prakriti.

Prakriti is constituted of three properties that are also its very substance, namely, Sattva or equilibrated transparency, Rajas or distraction and multiplicity, and Tamas or stability or fixity. The dynamics and statics of the scientist's world correspond to Rajas and Tamas, as two of the essences of Prakriti. The world of perception is not accustomed to visualise or experience Sattva, since all individual experience is dominated mainly by Rajas and Tamas. In rare moments of the cessation of the distraction of desire in the mind; Sattva manifests itself as a joyous experience. Sattva is both intelligence and bliss, which do not reveal themselves in a world of desire and action.

Prakriti manifests itself as several evolutes constituting the whole of creation. Purusha is infinite consciousness, and its action on Prakriti by a peculiar juxtaposition of itself with the ubiquitous Prakriti, stirs the properties of Prakriti, that is, Sattva, Rajas and Tamas, which are known as Gunas in the Samkhya terminology. The stimulation of the universal Sattva-Guna enables the Purusha to reflect itself on this Sattva which appears as Mahat, or Cosmic Intelligence. Mahat concretises itself into a Universal Self-awareness known as Ahankara. From Ahamkara proceed the five potentials of objectivity called Tanmatras, namely, Sound, Touch, Colour, Taste and Smell, in their Cosmic electromagnetic nature, which are concretised into the visible and solid substances of Ether, Air, Fire, Water and Earth. These five gross elements constitute the entire physical universe. So much is the objective universe.

Subjectively, the subtle potentials, such as sound and the like, while operating in the individual, in their essentiality as Sattva, become the causes of the sense powers of hearing, touching, seeing, tasting and smelling. As the compositions of the Rajas aspect of these potentials the active senses of speaking or vocal articulation, grasping, with hands, locomotion with feet, generation through the genitals and excretion through the anus are produced. The total of the Sattva elements of the potentials mentioned constitute the mind. These are the twenty-four principles of the Samkhya philosophy, beginning with Prakriti, and Purusha standing apart as Universal Consciousness. Prakriti and Purusha are both eternal and totally different from each other. Their coming together is the bondage of life through the sense of externality and individuality assumed by Purusha, which is otherwise universal, by an apparent contact of itself with Prakriti. The bondage of life in every one of its forms is due to the mixing up of the Purusha consciousness with the material evolutes of Prakriti. The separation of Purusha from Prakriti by knowledge and by the practice of Yoga is the liberation of the Purusha from entanglement in the processes of Prakriti and all its material and subtle expressions.

Among Western circles of philosophic thought, certain early Greek thinkers, and the famous expounders like Locke, Berkeley and Hume, as well as Bacon and Mill propound the philosophy of pure empiricism, holding that all value is externally placed and all knowledge is imported from outside, with no inherent or intrinsic a priors knowledge or final reality in the set-up of the individual. Even the Pragmatism made famous by William James is empirical in its approach and in its conclusions, together with its doctrine of utility being the test of truth. Sensory knowledge is of primary importance and all judgments, logical or rational, are based on information gained through sense-perception. The mind by itself has no knowledge of its own, it is like a clean slate on which is written sense-conditioned knowledge which is included in all that we know in science, psychology or psychoanalysis, aesthetics, education or morality, and all that is of any value in any way, such as religion and the code of ethics of human society.

Against this view is the rationalism of Plato and Aristotle, Descartes, Leibniz and Spinoza, Kant, Hegel, Bradley and Bosanquet, who emphasised that all knowledge is not empirical and that there is an inherent reason and spirit whose knowledge is a priori, and not a posteriori as the empiricists hold. Kant and Hegel, however, rose above the extremes of rationalism and empiricism and developed a transcendental philosophy blending together all that is true in the reports of the senses and all that is there in the mind and reason as inherent knowledge.

The empirical trend in terms of an acute psychological analysis by observation of the presence of suffering and sorrow caused by the linkage of 'Dependent Origination' (Pratitya-samutpada) in the working of the human psyche is to be found in the doctrine of the Buddha, and Buddhism. While this is one side of the matter, there is in this teaching a tremendous rational investigation not only delving into the ultimate causes of suffering but also into the possibility of there being a sure way out of suffering in the practice of the Eight Noble Virtues, whose elucidation is intensely spiritual, ending up in the transcendent recognition of the eternal state of Nirvana, or absolute blessedness, as the goal of all life.

The Mimamsa system of Vedic ritualism also falls into the category of empirical thinking in its insistence on certain types of semantic interpretation on the scriptural texts of the Veda and the very conception of the meaning of life as being not above the desire for happiness in a heavenly world of a multiplicity of gods.