West Bengal Chief Minister Mamata Banerjee on Thursday called upon one and all to stay united and fight against divisive forces."Unity in diversity is India's strength. We must all be united and fight against the forces which seek to divide us for selfish reasons," Banerjee tweeted.Referring to the philosophy of "Vasudhaiva Kutumbakam", meaning "the whole world is one family", Banerjee wrote: "On International Human Solidarity Day, let us pledge to uphold the spirit of 'Vasudhaiva Kutumbakam' in the truest sense."The United Nations General Assembly identified solidarity as one of the fundamental and universal values, and hence, it decided to mark December 20 of each year as the International Human Solidarity Day.