Posted based on a requested edit to this question
The modern "scientific method", perhaps as espoused in Karl Popper's "The Logic of Scientific Discovery", is seen today by many, especially in the West, as the "gold standard" for reliable investigation into the nature of reality. However, Buddhism -- in particular insight practices -- appears to propose an alternate approach to a similar goal. How do these methodologies compare, in terms of approach and reliability?
The main focus of this question is on "understanding reality", which is the domain of science. So, the first question is whether Buddhist insight meditation practice even qualifies as a science (i.e. a means of understanding reality).
From Wikipedia:
Science (from Latin scientia, meaning "knowledge") is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe. In an older and closely related meaning, "science" also refers to a body of knowledge itself, of the type that can be rationally explained and reliably applied.
So, the criteria for calling something science (at least by Wikipedia standards) are:
Buddhist insight practice fits all of these criteria; insight meditation is entirely systematic, it builds and organizes knowledge (more on knowledge later), its explanations and predictions are testable, it takes the universe (from a phenomenological POV) as its frame of reference, and it can be rationally explained and reliably applied.
So, Buddhist insight practice can at least be considered scientific.
Rather than focus on "which is better" (and get close-voted again), maybe we can agree to compare the two systems of "investigation into the nature of reality" objectively:
Approach
Buddhist insight takes as its paradigm a form of phenomenology or phenomenography, wherein:
there is only one world, one that is ours, and one that people experience in many different ways
It is therefore understood to be a means of understanding the nature of so-called "subjective" reality, i.e. one's own realm of phenomenological experience.
The modern scientific method, on the other hand, generally takes a stance of philosophical materialism, wherein:
matter is the fundamental substance in nature, and that all emergent phenomena (including consciousness) are the result of material interactions.
It is therefore understood to be a means of understanding the nature of impersonal material qualities from an "objective" (i.e. impersonal) point of view.
Reliability
Here's where the controversy arises, so hopefully we can avoid it to some extent by comparing the individual claims of reliability (somewhat) objectively and leaving the reader up to their own conclusions.
Material science relies upon quantity and quality of empirical data that is independent of an individual frame of reference (i.e. it must be reproducible in all circumstances, not affected by experimenter or subject bias). The certainty of its claims are therefore dependent on the perceived likelihood of the objectivity of the data supporting them. For all intents and purposes, this provides a fairly good understanding of the nature of reality; the ability to build upon and modify prior understanding has allowed for incredible breakthroughs in our ability to interact with the material world.
The potential downside to this reliance on impersonal data is that it can and often has led to dogmatic refusal to accept new methodology or even evidence (e.g. Einstein's refusal to accept quantum mechanics).
It also has as a limitation its own ability to perceive the universe as a whole (so far, for example, it can't). This sort of limitation is what Rupert Sheldrake gets at in his discussion of scientific dogmas. He lists ten dogmas currently held by the modern scientific community that may very well turn out to be false:
The point here is that the modern scientific method has led us to many of these dogmas through its locality - i.e. it can't say anything about the universe as a whole, except by inference, which may and often is proven wrong as new evidence is found.
A third point is that the modern scientific method tends to confuse data with truth and thus discard data that doesn't fit with a theory as statistical errors, etc. This is very well-documented (if somewhat outdatedly so) in The Book of the Damned, written in 1919. The author points out quite well the difference between what is commonly held as scientific knowledge and what is absolutely true, saying:
It is our expression that the flux between that which isn't and that which won't be, or the state that is commonly and absurdly called "existence," is a rhythm of heavens and hells: that the damned won't stay damned; that salvation only precedes perdition. The inference is that some day our accursed tatterdemalions will be sleek angels. Then the sub-inference is that some later day, back they'll go whence they came.
By damned, he means facts that have been ignored because they don't fit with contemporary scientific theory.
Again, practically speaking, the potential non-universality of modern scientific knowledge is inconsequential; for all practical purposes, it works.
Buddhist insight knowledge, on the other hand, is in a sense terribly "impractical", since it can only ever be "known" by the individual. As the Buddha said, the dhamma is "paccattaṃ veditabbo viññūhi" - to be realized by the wise for themselves.
It is also obviously unable to say anything about impersonal phenomena, since such entities are outside of its realm of observation and thus considered mental concepts.
On the other hand, it claims to provide a certainty of knowledge that material science does not (material scientists consider such certainty meaningless, since their frame of reference is impersonal). For example:
When endowed with five qualities, monks, in no long time a monk penetrates and intuits the Unshakeable. Which five? Here, monks, a monk is one who has attained discrimination of meanings, is one who has attained discrimination of principles, is one who as attained discrimination of language, is one who has attained discrimination of the illuminating qualities (of knowledge), and he reflects upon the mind as liberated. When endowed with these five qualities, monks, a monk in no long time penetrates and intuits the Unshakeable.
So, from a Buddhist point of view, insight meditation is preferable in the sense that it is not subject to alteration. The reason for this is it is also considered to be universal (from a point of view of one's own experience) - i.e., it is understood to be applicable to all entities in the universe (one's own universe of experience).
As someone pointed out in the earlier question, the two types of investigation are fairly non-competitive; material science focuses on material, Buddhist mental science focuses on the mind. The former is more useful for conventional purposes like curing disease and blowing stuff up. The latter is only useful for limited purposes like freeing oneself of all suffering.
Ok so I've read some of the comments. Here are my thoughts. Science strives to discover a truth that lies 'out there' independent of yourself. I don't think 'truth' in Buddhism means the same thing. And as far as I know there aren't any explanations in Science. Just descriptions. Might be the same in Buddhism, I do not know. Someone quoted Feynman above regarding his definition of the scientific method. In reality this is not how it happens. Sometimes theories are held on to even when they contradict observations. The best example of this is Newtons law of gravitation. There are new philosophical theories about how science actually work.(Sorry I cannot point you to any one in particular).
B. Alan Wallace writes extensively on this subject. See especially here. He initiated the International Shamatha Project to deploy applicable scientific methodologies to the study of Buddhist meditation. More to the point, he argues that Buddhist meditation, especially Vipassana, itself constitutes a science. In that, he follows William James, along with modern western philosophers such as Husserl, and even, to some extent, Wittgenstein.
A core point of Wallace is that the wholesale exclusion from rigorous study of internally observed events is: inappropriate; denying us of an extensive range of rigorous and repeatable observations of potentially profound use to humanity in understanding the nature of reality; and, perhaps most ironically, an example itself -- the exclusion -- of an unscientific approach.
Wallace doesn't ignore the problems of subjectivity, but he argues that in the same way that an expert physicist (say) is a different animal from the amateur with interest in science because typically the physicist undergoes extensive multi-year training after which the rest of the community can put some trust in their statements (e.g. sufficient trust to make it worthwhile attempting to repeat them), similarly expertly trained Vipassana (etc) practitioners are a different animal from amateur meditators, and because of their extensive training, we can put trust into their statements (again, sufficient trust to repeat them, and codify, and so on).
Specifically on this question, my personal experience is that while insight meditation has as its purpose an attainment of knowledge and experience of the fundamental nature of reality, natural science has two commonly held purposes, depending on who you ask. Most scientists today would say that it is the same purpose as Vipassana -- i.e. to figure out how things really are -- and, typically, that it is superior to Vipassana in that respect. A small subset including, for example, the physicist Bernard d'Espagnat, author of "Veiled Reality" (among several other books), argues that the fundamental nature of reality is essentially hidden (veiled) from us, the observer, and that all science can do is analyze and codify the inter-subjective interaction between whatever reality actually "is" (although at this stage the word is clearly richer and more subtle than at first sight), and whatever we, the observer, are. In other words, by contrast with the first (admittedly majority) group, the second group says that natural science is not really about figuring out how things are but rather is -- and can only ever be -- about how things appear.
Personally, I'm with Wallace and d'Espagnat (and Wittgenstein, and Hume, and Husserl, and Kant, and Scruton, and Ricard, and Hossein Nasr, and Nagarjuna, and even, on at least one point, Harris )
Let's explicitly define the terms in the OP's question "In terms of reliability of understanding reality, how does the scientific method compare with Buddhist insight practice?"
In general, we look for a new law by the following process: First we guess it; then we compute the consequences of the guess to see what would be implied if this law that we guessed is right; then we compare the result of the computation to nature, with experiment or experience, compare it directly with observation, to see if it works. If it disagrees with experiment, it is wrong. In that simple statement is the key to science. It does not make any difference how beautiful your guess is, it does not make any difference how smart you are, who made the guess, or what his name is — if it disagrees with experiment, it is wrong.
(Source: http://www.brainpickings.org/index.php/2012/05/11/richard-feynman-key-to-science/)
Does Insight Meditation reveal reality under the above definition? The answer is that it may. On the other we may simply imagine it, since it is a subjective experience. In my personal practice, I have subjective evidence from people who know me from before and after I started meditation that it has positively affected my behavior and mood. In addition, I have objective evidence in that I very rarely now have insomnia whereas before it was a weekly or even nightly event.
The scientific method is the simplest and most reliable way that we have to understand reality. I must emphatically separate the scientific method from the culture of scientists. The scientific method is organized skepticism and works whether you believe in it or not. It is capable of error and refuses to accept hypotheses can cannot be disproved. Falsifiability is a key criteria of scientific investigation.
If science proves some belief of Buddhism wrong, then Buddhism will have to change. In my view, science and Buddhism share a search for the truth and for understanding reality. By learning from science about aspects of reality where its understanding may be more advanced, I believe that Buddhism enriches its own worldview.
-- Tenzin Gyatso, the 14th Dalai Lama (Source: http://www.nytimes.com/2005/11/12/opinion/12dalai.html)
