Question: The Pure Land Tradition’s 8th Patriarch Great Master Liánchí (净土宗八祖莲池大师) taught in his ‘Commentary And Summary On The Sūtra In Which The Buddha Speaks Of Amitābha Buddha’《佛说阿弥陀经疏钞》that,
‘Now only upholding the name, this one method is sufficient and complete, with upholding the name being the same as upholding this one mind, with the mind complete with a hundred practices, the Four [Noble] Truths, Six Perfections and even the 84,000 Ganges’ sands’ dust motes, of all practice doors, as gathered without that not complete, thus is this method named as easy and feasible.’
How is Niànfó (念佛) related to the Four Noble Truths (四圣谛) and the Noble Eightfold Path (八正道)?
Answer: The below briefly explains the relations as enquired. (Do see too, the last two ‘Related Articles’ below, on the relations with the Six Perfections [六度].)
Four Noble Truths
 苦谛 First Noble Truth Of Suffering: There are four physical and four mental sufferings, as below. This is the nature of life and death in defiled lands [秽土] like ours here, which is why we practise Niànfó to reach Pure Land [净土], where there is no suffering at all. Before reaching Pure Land, suffering decreases with Niànfó practice as it creates meritorious virtues, that eradicates negative karma that causes suffering.
 集谛 Second Noble Truth Of Cause Of Suffering: All suffering arises from the Three Poisons (三毒) of attachment, aversion and delusion (贪瞋痴).  and  are the cause and effect of suffering respectively. In Pure Land, none of these poisons will be given conditions to arise. Before reaching Pure Land, these poisons decrease with Niànfó practice as it eradicates them.
 灭谛 Third Noble Truth Of End Of Suffering: All suffering ends with ending of attachment, aversion and delusion. This is experienced once Pure Land is reached. Before reaching Pure Land, the end of suffering becomes within reach in this lifetime with Niànfó practice.
 道谛 Fourth Noble Truth Of Path To End Of Suffering: All suffering ends with the Noble Eightfold Path, which can be practised with Niànfó too, as below. This is why we practise Niànfó, to transform greedy attachment (贪恋) to here, to be joyful seeking (欣求) of Pure Land, to transform aversion of here, to be revulsed renunciation (厌离) of this defiled land, and to transform delusion to wisdom, as Niànfó ‘opens wisdom’ (念佛开智慧).  and  are the cause and effect of suffering’s end respectively.
 生苦 Suffering of birth
 老苦 Suffering of ageing
 病苦 Suffering of sickness
 死苦 Suffering of death
 爱别离苦 Suffering of departure from the beloved
 怨憎会苦 Suffering from meeting the hated
 求不得苦 Suffering from not attaining the sought
 五蕴炽盛苦 Suffering from the Five Aggregates burning vigorously *
 色 Form
 受 Feelings
 想 Perceptions
 行 Mental Formations
 识 Consciousness
* All-pervasive subtle suffering through the Five Aggregates, that arises all the time in the background and/or foreground of experience, due to unskilful reaction to all conditioned things, with such ‘burning’ or being harmed fueled by the Three Poisons (三毒: attachment, aversion, delusion). Attachment and aversion are caused by delusional thinking of impermanent (无常) and unsubstantial (无我) mind and matter as permanent and substantial, not realising them to be empty (五蕴皆空). The first aggregate is of matter (身) of the Four Great Elements (四大) of earth, water, fire and wind (地水火风) and the other four are of mind (心).
Noble Eightfold Path
 正见 Right Understanding: of the Three Provisions (三资粮) of Faith, Aspiration and Practice (信愿行) to reach Pure Land.
 正思维 Right Thought: or motivation of learning, for true Practice (实行) of Niànfó with deep Faith (深信) and sincere Aspiration (切愿).  and  are of the learning of Wisdom (慧学), of the Threefold Learning’s (三学) third step, though some Wisdom is needed to start the Threefold Learning too.
 正语 Right Speech: with Niànfó, thus not lying (妄语), having double-tongued speech (两舌), useless speech (绮语) or harsh speech (恶口).
 正业 Right Action: without physical action during Niànfó, thus avoiding killing (杀生), stealing (偷盗) and sexual misconduct (邪淫).
 正命 Right Livelihood: with our full-time ‘job’ only being sincere Niànfó in the moment during Practice. ,  and  are of the learning of Precepts (戒学) or Morality, of the Threefold Learning’s (三学) first step.
 正精进 Right Diligence: of continual sincere Niànfó, thus avoiding all evil (诸恶莫作), practising all good (众善奉行) and self-purifying the mind (自净其意) with assistance of the Buddha’s Other-power (他力).
 正念 Right Mindfulness: of Āmítuófó’s name (阿弥陀佛) sincerely.
 正定 Right Concentration: by abiding peacefully upon only Buddha’s name (安住佛号), thus increasing in concentration. ,  and  are of the learning of Concentration (定学), of the Threefold Learning’s (三学) second step.
The One Method Of Upholding The Name Completely Gathers 10,000 Methods
Verse On One Method
The Principle Of ‘Vow Now For Birth Now’
(Relations Between The Four Noble Truths & Niànfó)
Great Master Liánchí: How Buddha Mindfulness Completes The Six Perfections (1)
Great Master Ǒuyì: How Buddha Mindfulness Completes The Six Perfections (2)
The Noble Eightfold Path In Pure Land
How Is Right Livelihood Practised In Pure Land?
Please be mindful of your speech, Amituofo!