This volume comprises the lectures given at the Fifth Anniversary Symposium held at the Institute of Mathematical Sciences, Madras, India, during January 1967. Professor Dallaporta of Padua delivered the inaugural address on the fundamental problem of quasars "whose study appears to hold im­ plications for cosmology." He presented a critical review of several attempts to understand their exceptionally large red shifts and also discussed the physical theories concerning the cause of the explosions which give rise to the quasars and to the tremendous energy output they require - questions which still remain unanswered. He stated, in concluding, that we may have to invoke certain aspects of the present theories of elementary particles in order to unravel these mysteries. Professor Mercier, well known for his studies on the philosophical foundations of modern physics, critically examined the various at­ tempts, such as that of Einstein, to formulate a unified field theory.