If the true is what is grounded, then the ground is not true, nor yet false. Wittgenstein, On Certainty Section 205
There’s two rival epistemological theories which we teach to our first years: foundationalism and coherentism. I wonder if these might be helpful in considering D&G’s rhizomatic and arborescent thinking.
The basic idea of foundationalism is that there is one fundamental truth, or set of truths, which underpin all other truths and which needs no further justification. Descartes was a classical foundationalist: he argued that his cogito (I think, therefore I am) was a fundamental, indubitable, self-evident truth upon which all other knowledge could be built. Descartes’ foundationalism reminds me of an upside down Eiffel tower – there’s an awful lot resting on one tiny truth. Euclidean geometry would be another example of a foundationalist set of principles. These are also, I think, examples of arborescent types of thinking: the cogito or Euclid’s axioms are the roots of the system and all other knowledge grows up and out from those (and is justified by being reduced to these first principles).
The basic idea of coherentism is that there is no one fundamental truth or set of truths which justify other truths. Instead of the hierarchy of knowledge of the foundationalists, coherentism suggests that knowledge consists of a web of beliefs, each of which is justified if it is consistent with other beliefs in the web. No one belief is epistemologically prior to other beliefs. Quine was a coherentist who rejected Descartes’ (and others’) “first” philosophy and argued that a sufficiently large circular chain of grounds could justify a belief. This, I think, compares to rhizomatic thinking.
If you think that truth needs to be justified according to a foundationalist model then you are left, as Wittgenstein says above, with first principles (like Euclidean axioms) that cannot themselves be justified. Or, like Descartes, forlornly stuck with his evil demon only able to repeat over and over “cogito, ergo sum”.
However, if you assume a coherentist model of justification, then a belief is justified if it does not contradict other beliefs in the web.
Neurath’s metaphor was popularized by W. V. O. Quine (Word and Object 1960, pp. 3-4); “Neurath has likened science to a boat which, if we are to rebuild it, we must rebuild plank by plank while staying afloat in it. The philosopher and the scientist are in the same boat. Our boat stays afloat because at each alteration we keep the bulk of it intact as a going concern.”
Of course, being a coherent set of propositions is not a guarantee of truth – the writers of Doctor Who try to ensure that they have a consistent set of facts but, sadly, the Doctor is not real.