Stream-enterer, as I said, is the first level of enlightenment. By definition, it has three basic conditions, or three fetters, which are destroyed. One is that a person totally lets go of the thought that following rules and rituals are the path to enlightenment. The second is the letting go of the concept of me being an individual self, the word Anatta. I cannot satisfactorily explain Anatta as from my understanding, it has to be experienced. Some translations of Anatta are no-self, not-self, voidness, emptiness, non-ownership. We don't actually own this body, we don't actually own the mind.
As defined, when a person becomes a Stream-Enterer they have actually penetrated the understanding of what Anatta means, that there is no permanent individual identity here. But apparently a Stream-Enterer does not hold that wisdom all the time. They understand it, then they lose it, they think of ego, they think they are someone. Occasionally they understand it again, they lose it. So, a Stream-Enterer understands it, loses it, in and out from time to time, but they have penetrated it at least once. The fully enlightened person called the Arahant or Buddha understand it all the time but that is a different quality.
The third fetter that they have destroyed is any doubt regarding the Triple Gem, the Buddha, the Dhamma, and the Sangha being the definite way towards enlightenment. They have absolutely no doubt because they have penetrated, they know. So, there is simply not a single trace of doubt regarding the Triple Gem. By definition those are the three qualities of someone who is a Stream-Enterer.
Now how to become a stream-enterer is to develop your Paramis, develop your wisdom especially. Try to penetrate through this thought that it is me, me, I, I, the center of the world, and so on. Try to understand the qualities of the Buddha, Dhamma, Sangha, so you can develop more Saddha, more confidence, more deep faith in the Triple Gem. Continually look at this understanding that rules and rituals themselves are not a path to enlightenment. So that is how you are going to work towards it.
As to "how do you recognize the stream-entry?", from what we have read and have been told by some of our teachers, if you become Streamer-Enterer, you know it. If someone has to tell you that you are, then you aren't. Now as much as you might find this incredible, unfortunately there are some teachers who are going around telling some of their students they are Stream-Enterers. I, myself, was told I was a Stream-Enterer with my first big concentration experience. It was merely a concentration experience, just a phenomena of the mind. It felt very pleasant, I asked one teacher about it and they told me I was a Stream-Enterer. I didn't believe it. Fortunately there were two teachers, I asked the other teacher, and they explained the concentration experience. I think, oh good, that is all I had. Do be aware that there are actually some teachers going around telling their students that they have actually done it. If you have done it, it is said, you are going to know.
How possible is it for lay people in the West to become a Stream-Enterer? According to what I understand, yes, possible. However, the Buddhist teachings that we are learning now are 2,500 years old. It is taught, and it must happen because of impermanence, that these particular teachings will eventually disappear one day. According to some commentaries it is going to be 5,000 years, that these particular Buddha's teachings exist and then they disappear. They disappear and then much time goes by, and then another Buddha arises, starts teaching again and the same thing happens over and over.
Now, it's taught, that as the teachings travel through 5,000 years, slowly it simply decays, just like a human body, just like everything else. So, originally when the Buddha was alive we had thousands and thousands of enlightened people, a Golden Age. And they say it always is when a Buddha is alive because that is the gift of being able to have high Paramis, you get born with a Buddha. For those of us here, we may have had some good Paramis, we might have been there but we didn't catch it, did we? So here we are still working on it. We can say that we are late for Siddhattha Gotama, or we can say that we are early for the next one.
So, whether it is possible or not, I don't know, but as the teaching goes through this 5,000 or so years it slowly decays. They say that the Monkhood itself starts to become corrupt. One hundred years after the Buddha died, that started. There was a split in the Monkhood. Believe it or not the argument, and this is historically written by the historians, the argument that started the very first split was that some monks wanted to carry salt so they could flavor their food. That started it. So, those monks set up their own group because the real monks didn't keep salt, as that would be an obvious sense desire, right?! That was the first split.
After 300 years went by, I believe, there were 16 different schools in Buddhism, according to historical accounts. Out of those 16, two of them continue today. We have the Theravadin Buddhist School in Thailand, Sri Lanka and so on. We have the Mahayana school, which is Tibet, China, Japan, etc. So two of them came out of those 16. Theravadin has proven historically to be the most pure, it follows what the Buddha did in his days as much as possible. We can see there is a deterioration going on as to what the Buddha set up so that monks, say in Japan, can get married and have kids, which is certainly not what the Buddha taught.
So, first the Monkhood starts to deteriorate. Then the teachings start to deteriorate because the monks, and we can include the nuns here, too, who are doing the teaching are not so pure themselves. So the teachings start to deteriorate. Next, the ability to become an enlightened person, first the Arahant, the fully enlightened people, they disappear, there is no more chance for full enlightenment. Then the non-returner, then the once-returner, then the stream-enterer disappears. We can still develop Paramis though. Whether it is possible to become partly or fully enlightened isn't a major problem, we can still develop Paramis. So, even as the teachings start to decay, we still have to keep our work going.