According to the official rules of pinyin, should 道德经 be transcribed with or without spaces between the individual syllables? While reading the Wikipedia article about the 道德经 / 道德經, I noticed how inconsistent it is in its pinyin transcription of that book title. Here are the transliterations found in the article (the link in the previous sentence intentionally points to the current version, since the inconsistency may be edited out of the article at some point after the submission of this question):

Dàodé Jīng
Dao De Jing
Dàodéjīng
Daodejing (e.g. &quot;The title &quot;Daodejing&quot;, with its status as a classic, was only first applied from the reign of Emperor Jing of Han (157–141 BCE) onward.&quot;)

I am intentionally ignoring the Wade-Giles transcription. That the transcription sometimes includes tone diacritics (for those familiar with pinyin) and sometimes does not (for those who don't know what those dashes mean) is something I can also live with. My concern is the inconsistency in the use of spaces between individual syllables. Previously, I assumed that 道,德 and 经 were three different words, since disyllabic words were rare in Classical Chinese (they were typically loanwords); hence I expected a transcription that uses spaces between each syllable: dào dé jīng (ignoring capitalisation).
However, the Wikipedia article also uses a transliteration without a space between the first two syllables and adds: 'Compare the compound word 道德 (pinyin: dàodé; Wade–Giles: tao⁴-tê²), literally &quot;ethics&quot;, &quot;ethical principles&quot;, &quot;morals&quot; or &quot;morality&quot;.'
Do the official rules of pinyin favour one transliteration (especially &quot;dào dé jīng&quot;) over other ones (especially &quot;dàodé jīng&quot;)? Do these rules also take into account whether a book title is in Classical Chinese or in modern putonghua? (I add the second question in case 道德 turns out to be a more recent concept than the 道德经 itself.)
Most of foreigners use emphasized text &quot;Tao Te Ching&quot;. Of course, it's not in Mandarin Chinese Pinyin, but in old Chinese Pinyin. It is very common, such as Peking and Sun Yat-sen. And, how to write it in Mandarin Chinese Pinyin?
Rules:
There should be a space between two words what mean different.
《现代汉语词典》 Xiàndài Hànyǔ Cídiǎn
《毛主席语录》 Mao Zhuxi Yulu
《市民准则》 SHIMIN ZHUNZE
Here's the exact rule:

书报名、标题名可以全部大写，也可以每个词开头的字母大写，有时为了美观，可以省略声调符号。如：
儿童文学 ERTONG WENXUE
《现代汉语小词典》，复旦大学出版社，P1011

To solve this problem, we need to know is &quot;道&quot; and &quot;德&quot; in one word, or have different meaning. I searched for it, and got to know:
&quot;道&quot; is &quot;天地万物的演化运行机制(The evolutionary operating mechanism of the universe)&quot;.
&quot;德&quot; is &quot;人的素质或者事物品质(Quality of people or things)&quot;.
Also, there are two parts in &quot;Tao Te Ching&quot;, 《道经》 and 《德经》. So, it should be &quot;Dao De Jing&quot;.
Why not &quot;Daode Jing&quot;?
In modern Chinese, &quot;道德&quot; is one word, means &quot;人们共同生活及其行为的准则和规范(The rules and norms of people living together and their behavior)&quot;. It's different to &quot;道德&quot; in《道德经》.
Actually, you can also translate it yourself. For example, you can translate it into &quot;Theory of Everything and Code of Conduct in all the Time in Life&quot;(my bad translation). But I still think &quot;Tao Te Ching&quot; is the best choice because it is common. When people see this title, they knows which book it is in a few seconds.