Some philosophers of biology such as James G. Lennox have argued that Darwin was a teleologist,[44] while others like Michael Ghiselin described this claim as a myth promoted by misinterpretations of his discussions, and emphasized the distinction between using teleological metaphors and actually being teleological.[45] Michael Heads, on the other hand, describes a change in Darwin's thinking about evolution that can be traced from the first volume of On the Origin of Species to later volumes. For Heads, Darwin was originally a far more teleological thinker, but over time, "learned to avoid teleology." Heads cites a letter Darwin wrote in 1872, in which he downplayed the role of natural selection as a causal force on its own in explaining biological adaptation, and instead gave more weight to "laws of growth," that operate [without the aid of natural selection].[46]