In philosophy, metaethics is the branch of ethics that seeks to understand the nature of ethical properties, and ethical statements, attitudes, and judgments. It is one of the three branches of ethics generally recognized by philosophers, the others being ethical theory and applied ethics. Metaethics has received considerable attention from academic philosophers in the last few decades.

While normative ethics addresses such questions as “What should one do?”, thus endorsing some ethical evaluations and rejecting others, metaethics addresses questions such as “What is goodness?” and “How can we tell what is good from what is bad?”, seeking to understand the nature of ethical properties and evaluations.

Some theorists argue that a metaphysical account of morality is necessary for the proper evaluation of actual moral theories and for making practical moral decisions, however others make the reverse claim that only by importing ideas of moral intuition on how to act can we arrive at an accurate account of the metaphysics of morals.

A second area of metaethics involves the psychological basis of our moral judgments and conduct, particularly understanding what motivates us to be moral. We might explore this subject by asking the simple question, “Why be moral?” Even if one is aware of basic moral standards, this does not necessarily mean that one will be psychologically compelled to act on them. Some answers to the question “Why be moral?” are to avoid punishment, to gain praise, to attain happiness, to be dignified, or to fit in with society.

Agapism professes that love  should be the sole ultimate value and that all other values are derived from it, or that the sole moral imperative is to love. Theological agapism holds that our love of God is expressed by loving our fellow man. As the ethics of love, agapism indicates that we should do the most loving thing in each situation, letting love determine our obligation rather than rules. Alternatively, given a set of rules, agapism indicates to follow those rules which produce the most love.

The American philosopher Charles Sanders Peirce used the word agapism for the view that creative love is operative in the cosmos. Drawing from the Swedenborgian ideas of Henry James, Peirce held that it involves a love which expresses itself in a devotion to cherishing and tending to people or things other than oneself, as a parent may do for offspring, and as God does especially for the unloving, whereby the loved ones may learn.

Peirce regarded this process as a mode of evolution of the cosmos and its parts, and he called it agapism, wherein: “The good result is here brought to pass, first, by the bestowal of spontaneous energy by the parent upon the offspring, and, second, by the disposition of the latter to catch the general idea of those about it and thus to subserve the general purpose.”

Comfort noise is artificial background noise used in radio and wireless communications to fill the silence in a transmission resulting from voice activity detection or from the audio clarity of modern digital lines.

Some modern telephone systems such as wireless and VoIP use voice activity detection, a form of squelching where low volume levels are ignored by the transmitting device. In digital audio transmissions, this saves bandwidth of the communications channel by transmitting nothing when the source volume is under a certain threshold, leaving only louder sounds such as a speaker’s voice to be sent. However, improvements in background noise reduction technologies can occasionally result in the complete removal of all noise.

The result of receiving total silence, especially for a prolonged period, has a number of unwanted effects on the listener, including the following:

• The listener may believe that the transmission has been lost, and therefore hang up prematurely.
• The speech may sound choppy and difficult to understand.
• The sudden change in sound level can be jarring to the listener.

To counteract these effects, comfort noise is added, usually on the receiving end in wireless or VoIP systems, to fill in the silent portions of transmissions with artificial noise. The noise generated is at a low but audible volume level, and can vary based on the average volume level of received signals to minimize jarring transitions.

In modern VoIP products, users may control whether they want comfort noise enabled or disabled. During the siege of Leningrad in 1942, the beat of a metronome was used as comfort noise on the Leningrad radio network, indicating that the network was still functioning.

Grapheme-color synesthesia is a form of synesthesia in which an individual’s perception of numbers and letters is associated with the experience of colors. Like all forms of synesthesia, grapheme-color synesthesia is involuntary, consistent, and memorable. It is one of the most common forms of synesthesia, and because of the extensive knowledge of the visual system, one of the most studied.

One recent study has documented a case of synesthesia in which synesthetic associations could be traced back to colored refrigerator magnets. Despite the existence of this individual case, the majority of synesthetic associations do not seem to be driven by learning of this sort. Rather, it seems that more frequent letters are paired with more frequent colors, and some meaning-based rules, such as B being blue, drive some synesthetic associations.

These experiences have led to the development of technologies intended to improve the retention and memory of graphemes by individuals without synesthesia. Computers, for instance, could use artificial synesthesia to color words and numbers to improve usability. Individuals with grapheme-color synesthesia rarely claim that their sensations are problematic or unwanted. In some cases, individuals report useful effects, such as aid in memory or spelling of difficult words.

Synesthetes often report that they were unaware their experiences were unusual until they realized other people did not have them, while others report feeling as if they had been keeping a secret their entire lives. Many synesthetes can vividly remember when they first noticed their synesthetic experiences, or when they first learned that such experiences were unusual. Writer and synesthete Patricia Lynne Duffy remembers one early experience:

“One day, I realized that to make an R all I had to do was first write a P and then draw a line down from its loop. And I was so surprised that I could turn a yellow letter into an orange letter just by adding a line.”