The paper aims to elucidate Herbert Spencer's attitude towards the evolutionary thought of Jean-Baptiste Lamarck. According to a common misunderstanding, Spencer's view of evolution, in its endorsement of the inheritance of acquired characters, was nothing but a different form of Lamarckism. Such a description, while stressing a relevant feature of Spencer's perspective, still impoverishes his view by forcing it into an inadequate interpretative framework: the clash between Darwinians and Lamarckians. The quarrel between these two schools of evolutionists, not only was subsequent to the development of Spencer's thought, but was also confined to a limited number of biological concerns which by no means exhaust the extent of Spencer's philosophical evolutionism, whose aspiration was to explain not merely organic evolution but the whole cosmic development. Moreover, even considering solely the biological side of the matter, there are two aspects of Spencer's perspective which render it quite irreducible to Lamarck's. Firstly, while Lamarck had founded his own account of evolution on the particular features of living beings, Spencer referred evolutionary change to the fundamental transformations of force, matter and motion, thus explaining evolution in physical terms. Secondly, while Lamarck had seen in life an inherent tendency to advance towards more complicated forms, Spencer explicitly rejected such hypothesis reducing all evolutionary progress to a form of adaptation. Nonetheless, in order to avoid a seemingly theologically-oriented conception of evolution, he embraced the equally slippery view based on the idea of a growing ‘harmony' between organisms and environments. The paper will focus on the explanation of these two main points.