I start out this thread having only a hazy notion of Uniformitarianism, (henceforth U). What I understand of it is that the processes which we can observe today occur more or less at the same rate and in the same manner as they have always done and will. As I also understand it, the basis for holding to U is that the observed data backs up the intial presumption. Edit: From msg 61 linked in Percys msg below, U is made up of the following 4 elements:
Uniformitarianism, as defined by Lyell, consists of four principles:
1. uniformity of law
2. uniformity of process (actualism)
3. uniformity of rate (gradualism)
4. uniformity of state (steady-statism)
(I'm not sure to what level each branch of historical science holds to each of these elements. Percy's link (msg 61)indicated that geologists for example, only hold to elements 1 & 2 )
Whilst recognising that one may feel one has to start somewhere and if one doesn't it raises questions about what one could tell about the past:
Accurate, direct data that indicates processes to have operated according to U is restricted to say the last 100 years or so (although there may be problems with even this). Given the current age of the earth is estimated at 4.5 billion years old, the data only covers 1/45,000,000th of the total amount. Thus, this data represents only a dot on the graph (which is presumed to be a straight line stretching backwards and forwards from this point). This seems, in itself, to be an insufficent basis for saying anything about the validity of U.
The comments I have heard thus far (about ice layers and radioactive dating) all seem to suffer from the same weakness, to whit: they all seem to start out with the presumption of U and analyse the data in the light of it. There seems to be a certain amount of wiggling out of this by stating the position as: "We observe and this is what we would expect to see if U was valid - we don't go out with the presumption". Investigating the validity of that approach would, I imagine, be one outworking of this thread.
If there was no objective, non-U derived basis for stating U to be valid then how is U stated to be valid? Is U just an arbitary starting point, chosen for philosophical rather than objective reasons? If so, does that mean every conclusion drawn on the basis of U is an arbitary one? In other words, though the puzzle can be arranged in one fashion if U is presumed, could the data not equally fit together with the same level of tentiveness had another arbitary, non-U set of conditions occurred.
I don't propose to discuss alternative hypothetical conditions per se - given that if the data has been analysed for so many years in the light of a presumption of U, then no other conditions can hope to compete directly. Not that that is a reason to suppose U is valid. Another outworking of the thread would be discussion around the validity of "authority of the data" argument - should it transpire that all the data is based on an initial, non-objective presumption.
This message has been edited by iano, 16-Sep-2005 01:22 PM