I am increasingly thinking of 'truth' as a misleading and undefinable concept. For one thing, just because some statement are true, that does not provide a reason for postulating that there is a meaningful abstract noun 'truth'. 'True' is (at most) a predicate, an adjective modifying the proposition being discussed - making it a noun is simple reification. Defining 'truth' only creates a 'thing' that we can argue about. We can instead ask 'What does it mean for a proposition to be true?'. Secondly, in science, 'truth' was replaced by 'certainty' by Descartes, which was later replaced by 'confidence', reflecting the lack of total certainty of anything other than that, updating Descartes, 'there is thinking, therefore there is thinking'. Describing something as 8 ft long means that we expect, with 95% confidence, that the length of the 2x4 is between 8 - delta and 8 + delta feet long, where delta is situation specific, and can be either explicit or specified.

Interesting discussion of how we characterise objects in 'Women, Fire and Dangerous Things' by Lakoff. A tree is recognised as a tree because it is similar to objects that have been previously characterised as trees.

We can know with 100% that pain exists. Could we tell we are high or depressed if we cannot be sure of our comparisons with not-high or not-depressed?

I object to quantifying uncertainty as a percentage or fraction. In order to calculate a probability, you need a model and a set of assumptions. You are saying that 'Given my model is right and my assumptions are correct, the probability is x%. 'I assume that the coin is fair, and that an infinite number of coin flips under these specific circumstances would yield an even number of heads and tails.......' Otherwise the percentage that you quote is only a statement of your emotional commitment. The existence of anything beyond the perception of thinking is something for which evidence is not available, but it can still be accepted as a 'working hypothesis'.

I do not accept 'I think therefore I am'; I do not see how you can assume that thinking necessarily implies a thinker. We have a prejudice that verbs require a subject, which can sometimes require some linguistic acrobatics. What is the 'it' in 'it is raining'? By assuming that thinking implies a being that is doing the thinking, you are begging the question. The best you can do is to say something like 'thinking, therefore thinking'.

I think this is a good perspective - there is a set of procedures, methods and attitudes that are recognised as fitting the standards of the community, such as objectivity and requiring p-values to be less than 0.05. In addition to journal articles and textbooks, these standards are passed down and enforced by teachers, advisors, colleagues, reviewers and editors. People who do not adhere to these standards will (generally) be limited in their ability to publish and obtain funding.

As a scientist, I do not know of anyone who uses a 'scientific method'. Imagine a private investigator trying to solve a case. They can build on the experience of themselves and others, but ultimately they will use whatever currently legitimate tools are available. The thing that makes science science are the activities of a community of self-identified members who are recognised as such by other members of the community who share a particular set of approaches, values and standards, that shifts as their perspectives change. Primary values of this community are a belief in the provisional nature of our knowledge and, as Whitehead puts it, 'a vehement and passionate interest in the relationship of general principles to irreducible and stubborn facts'. These values also currently include quantification, objectivity and replicability, but these are only included as they are seen as furthering this relationship between principles and facts.