The Pali term nimitta, means a “sign," i.e., the idea or image conceived, or an object perceived. The keeping in mind of a nimitta, and maining it is a sign of concentration. When you develop an anapanasati nimitta (i.e., that of the breath), and practice it further, then you need a good knowledge of teachings (suttas) for you to overcome obstacles that you face. The ‘nimitta’ is your main object of focus. When the hindrances are being overpowered by the jhana factors inwardly, on the side of the nimitta too certain changes are taking place. The original object of concentration, i.e., in the mindfulness of breathing the touch sensation of the breath, with the strengthening of concentration the breath gives rise to another object called the "learning sign" (uggaha-nimitta).
For the breath it will be a reflex image arisen from the touch sensation of the air currents moving around the nostrils. When the uggaha-nimitta appears, the meditator leaves the breath nimitta and fixes his attention on this new object. In due time still another object will emerge out of the uggaha-nimitta. This is called the "counterpart sign" (patibhaga-nimitta). It is a purified mental image many times brighter and clearer than the uggaha-nimitta.
These nimittas can be either beneficial or harmful, true or false, so we shouldn't place trust in them. That is why before getting into meditation, one should be very clear of the purpose for the meditation. It should be solely for the aim of attaining Nibbhana. Then you will not give into these distractions. When meditating alpha brainwave is produced in you when your body calms down and your mind is completely relaxed. Your brain's thinking is slower, your mind is clear and you may even feel slightly drowsy. If you are not firmly grounded on Anicca, Dukkha, Anatta you tend to cling in to these without contemplating the impermanency of these. If we're thoroughly mindful and alert, they can be beneficial, as you are firmly grounded on Anicca, Dukkha, Anatta. But if our powers of reference are weak or if we lack strength of mind, we're likely to follow the drift of whatever images appear, sometimes losing our bearings to the point where we latch on to the images as being real.
The uggaha-nimitta can be experienced in some peoples normal life too. The worldly knowledge is of two types – one that comes from studying books or ones that comes from thinking things through. This second kind of knowledge arises within the mind itself. People who are trained in the theoretical sciences work with their thinking. They think to the point where an idea appears as a picture in the mind, like an uggaha-nimitta (spontaneous image). When the picture appears in the mind, they may sketch it down on paper, and then experiment with physical objects to see if it works. If it doesn't work, they make adjustments, creating a new idea from their old idea — keeping at it until they find what works in line with their aims.
- Critical thinking takes place in a mental environment consisting of our experiences, thoughts, and feelings. Some elements in this inner environment can sabotage our efforts to think critically or at least make critical thinking more difficult. Fortunately, we can exert some control over these elements. With practice, we can detect errors in our thinking, restrain attitudes and feelings that can disrupt our reasoning, and achieve enough objectivity to make critical thinking possible.
- The most common of these hindrances to critical thinking fall into two main categories: (1) Those obstacles that crop up because of how we think and (2) those that occur because of what we think. The first category is comprised of psychological factors such as our fears, attitudes, motivations, and desires. The second category is made up of certain philosophical beliefs.
- None of us is immune to the psychological obstacles. Among them are the products of egocentric thinking. We may accept a claim solely because it advances our interests or just because it helps us save face. To overcome these pressures, we must (1) be aware of strong emotions that can warp our thinking, (2) be alert to ways that critical thinking can be undermined, and (3) ensure that we take into account all relevant factors when we evaluate a claim.
- The first category of hindrances also includes those that arise because of group pressure. These obstacles include conformist pressures from groups that we belong to and ethnocentric urges to think that our group is superior to others. The best defense against group pressure is to proportion our beliefs according to the strength of reasons.
- We may also have certain core beliefs that can undermine critical thinking (the second category of hindrances). Subjective relativism is the view that truth depends solely on what someone believesâa notion that may make critical thinking look superfluous. But subjective relativism leads to some strange consequences. For example, if the doctrine were true, each of us would be infallible. Also, subjective relativism has a logical problemâit’s self-defeating. Its truth implies its falsity. There are no good reasons to accept this form of relativism.
- Social relativism is the view that truth is relative to societiesâa claim that would also seem to make critical thinking unnecessary. But this notion is undermined by the same kinds of problems that plague subjective relativism.
- Philosophical skepticism is the doctrine that we know much less than we think we do. One form of philosophical skepticism says that we cannot know anything unless the belief is beyond all possible doubt. But this is not a plausible criterion for knowledge. To be knowledge, claims need not be beyond all possible doubt, but beyond all reasonable doubt.