Indian Philosophy: Origins, Meaning and General Characteristics; Vedic and Upanishadic Thought
Origins and meaning
Indian philosophy (darśana, 'seeing') grows from Vedic ritual and Upanishadic inquiry. The four Vedas-Ṛg, Sāma, Yajur, Atharva-contain hymns, ritual manuals, forest treatises and Upanishads. Śruti is revealed hearing; smṛti is remembered tradition. The Upanishads turn from petitioning gods to asking what grounds sacrifice, speech and self: Brahman, Ātman, karma, saṃsāra and mokṣa.
General characteristics
Most schools accept pramāṇa (valid knowledge), rebirth and liberation, but disagree over authority and method. The six āstika darśanas-Nyāya, Vaiśeṣika, Sāṃkhya, Yoga, Mīmāṃsā and Vedānta-cite Vedic authority. Cārvāka, Jainism and Buddhism are nāstika because they reject that authority; nāstika does not simply mean 'atheist'. Common debates concern the self, causation, perception, inference and the means to freedom.
Worked example
Bṛhadāraṇyaka's 'neti neti' ('not this, not this') negates the self as body, breath, mind and intellect. Reasoning: whatever is an object of changing experience cannot be the unchanging witness; the body is an object, so it is not Ātman. Negation removes false identifications, leaving the witness that cannot itself be objectified. Advaita then reads 'tat tvam asi' as essential identity of Ātman and Brahman; rival schools read the same sentence differently.
Traps
Do not say the Upanishads teach creation from nothing, or that āstika means 'theistic'. Do not treat Vedic religion as already monotheistic or the Upanishads as anti-Vedic. Avoid using 'Hindu philosophy' as a single doctrine, and do not confuse śruti with smṛti.