Many elements of the modern American creationist movement would be familiar to Darwin, especially the argument from design, which of course was very well known (and well-regarded) by educated people of his time. Young-Earth creationism, on the other hand, would be puzzling to him; Bishop Ussher's 4004 BCE age of the Earth was not considered mainstream Christian theology in the late 19th century, though certainly the view had its adherents among clergy. Darwin might have heard of the “scriptural geologists” who promoted a young-Earth view during the 19th century, but like other scientists of his time, he would have ignored them. The current creationist strategy of disclaiming evolution as weak science would have seemed more familiar to him, given the criticisms of evolution he encountered during his own time.