India has long been distancing from partcipating in Quad or any grouping which can be construed as purpose for countering China. For long time, India's foreign policy was toward establishing strong neighbourhood first policy without creating any confrontation with China. But, recently after Xi Jingping's accession as President and his aggressive policy of neo-agressive policy of competing with US on economy front and pushing herself as Asia's super power. In 2008, India withdrew from the plan of joining the Quad(US, Australia and Japan) showing it's stance toward Non-alignment policy.
But, Now India is also now seen getting away with diplomatic shyness of openly speaking against China on following issues:
1. Doklam confrontation.
2. In Aksai Chin confrontation of PLA
3. India giving support toward Permanent Court of Arbitration judgement on South China Sea.
All such instances illustrates that India has moved from passive principle of not confronting China to active steps with purpose and process.
Other points to support the case:
1. Recent episode of India agreeing to join Quad
Reason: India realising the power of cooperation with Like Minded nation even though China claiming it as "Asian NATO". Such coopeartion will make India's Prermanent memebership claims strong as well as equip defence technology and free navigation policy in SCS and Indian ocean.
2. India openly supporting Brunei, Phillipines, Malaysia, Taiwan and Vietnam for their sovereignity, transparent mechanism to decide ownership of islets and domination by China in SCS.
3. India not showing diplomatic interests on OBOR(One Belt One Road) and MSR(Maritime Silk Route)
4. India tactfully strengthented ties with coastal nations along the String of Pearl to weaken China's intention.
5. India openly opposing and questioning the CPEC geographical validity. US also recognised in UN proceedings the purpose of India.
CONCLUSION:Hence, the underlying principle of Quad is to establish confidence among smaller coastal/seabound nations along Indian Ocean and SCS against China. This principle is also in line with India's policy of: Neighbourhood first policy and Act East policy. Also, it will help India take greater role in Asia's leadership.
