In most systems of cartomancy with playing cards, the fours are cards of stability. However, a further connotation that I think attaches to them is that of pact or agreement between parts. Possibly this is due to the four pips resembling the legs of a table where people sit to talk.

The Four of Hearts is the card of reunions, gatherings and positive social occasions. It is also a symbol of agreements that come easy or are easily restored (Hearts): harmony and affinity all play into the meaning of the card. Because of the emotional connotation of the suit, the card can signify sex.

The Four of Clubs represents talks, and it is mainly the conversation card. However, it is not splendid. Because of the neutral nature of the suit of Clubs, which implies struggle and the need for action, the Four can go either way: toward agreement or toward breakup. It implies a degree of difference that needs to be reconciled, which is why talks are necessary. It’s not a bad card, but it is open-ended.

The Four of Diamonds is the card of formal agreements. It represents all things to do with papers, documents, offices, etc. Because the suit is more material than that of Hearts, the agreement can be interpreted as a transaction, and therefore the card represents buying and selling, and, by extension, all objects. In general, it signifies economic activity and has an affinity with the more material side of life.

The Four of Spades takes the basic theme of the number and runs it into the ground. The card represents loneliness and isolation. It shows the inability to get along or reach a positive conclusion. It shows complete disharmony and the impossibility of proceeding in a given direction, thus implying blockage. With other negative cards it means failure and trouble that cannot be overcome.