These thoughts do not mean anything. They are like
the things I see in this room [on this street, from
this window, in this place].

Unlike the preceding ones, these exercises do not begin with the idea for the day. In these practice periods, begin with noting the thoughts that are crossing your mind for about a minute. Then apply the idea to them. If you are already aware of unhappy thoughts, use them as subjects for the idea. Do not, however, select only the thoughts you think are "bad." You will find, if you train yourself to look at your thoughts, that they represent such a mixture that, in a sense, none of them can be called "good" or "bad." This is why they do not mean anything.
In selecting the subjects for the application of today's idea, the usual specificity is required. Do not be afraid to use "good" thoughts as well as "bad." None of them represents your real thoughts, which are being covered up by them. The "good" ones are but shadows of what lies beyond, and shadows make sight difficult. The "bad" ones are blocks to sight, and make seeing impossible. You do not want either.
This is a major exercise, and will be repeated from time to time in somewhat different form. The aim here is to train you in the first steps toward the goal of separating the meaningless from the meaningful. It is a first attempt in the long-range purpose of learning to see the meaningless as outside you, and the meaningful within. It is also the beginning of training your mind to recognize what is the same and what is different.
In using your thoughts for application of the idea for today, identify each thought by the central figure or event it contains; for example:

This thought about ---- does not mean anything.
It is like the things I see in this room
[on this street, and so on].

You can also use the idea for a particular thought that you recognize as harmful. This practice is useful, but is not a substitute for the more random procedures to be followed for the exercises. Do not, however, examine your mind for more than a minute or so. You are too inexperienced as yet to avoid a tendency to become pointlessly preoccupied.
Further, since these exercises are the first of their kind, you may find the suspension of judgment in connection with thoughts particularly difficult. Do not repeat these exercises more than three or four times during the day. We will return to them later.

- Jesus Christ in A Course in Miracles, Lesson 4